These fun Halloween Lime Slime Cupcakes are neon green lime cupcakes filled with a lime curd colored green for the slime effect and topped with green American buttercream. It's a little gross with the oozing slime center and the neon green frosting, but they're so delicious and kids will go crazy for them!
I've had slime cupcakes on my list for quite some time for a fun Halloween dessert. I finally am able to check it off my long list of seasonal recipes to make.
If you haven't noticed, I love a good spooky dessert. Take a look at this Spooky Spiderweb Cake with a neon green marshmallow creme web on it or these Poison Apple Cake Pops with a touch of sparkly glam from the black sanding sugar.
I think one of my favorites though are these Bloody Red Velvet Rice Krispie Treats. They're gross, delicious, and pretty darn messy.
Slime Cupcake Ingredients
These lime slime cupcakes have many ingredients since everything is made from scratch. I'm going to break it down into components.
The lime curd is the perfect filling to resemble slime and the fact that lime and slime rhyme is even more perfect.
See the recipe card for quantities.
- large eggs - for this recipe you'll be using the egg yolk and the egg white.
- granulated sugar - also known as white sugar.
- salt - this helps balance the sweetness.
- lime juice - since we need lime zest, I would recommend using fresh limes, but you could also use Nellie and Joe's Key Lime Juice which you can find in the juice section of your grocery store.
- lime zest - lime zest is a must! It adds so much flavor. Avoid grating the pith though (the white part that's just underneath the green on the lime peel. That's bitter.
- butter - This helps cool the curd down and also provides a creaminess.
- neon green food coloring - I always recommend the gel food coloring but you can use the yellow and green liquid food coloring instead.
See the recipe card for quantities.
- butter - you can use salted butter just reduce the salt in the recipe by half.
- granulated sugar - white sugar
- egg whites - about 3 large eggs worth.
- vanilla Greek yogurt - plain green yogurt or full-fat sour cream will work as well
- milk - use whole milk for this recipe.
- lime juice - We'll be using the zest of the lime in the cupcakes, so squeeze the juice out of the fresh limes to use as well. If you want to use bottled lime juice, I recommend this key lime juice.
- vanilla extract - use your favorite store-bought vanilla extract or a good homemade vanilla extract
- lime zest - have a zester on hand to zest your citrus. Be sure to not zest the pith of the lime though.
- Green food coloring - Use the gel food coloring if you have it. If not, a green and yellow mix of the liquid food coloring will work.
- all-purpose flour - Be sure to fluff the flour first. I do this by scooping it several times and sprinkling it back out before scooping and leveling my flour.
- baking powder - the leavening agent for fluffy cupcakes. Baking powder is used because there's acid in the recipe to activate it.
- salt - This helps balance the sweetness of the cupcake.
How To Make Slime Cupcakes
There are several steps to this oozing cupcake, but the end results will wow your kids especially since it's tasty.
Step 1: Whisk the eggs, sugar, salt, lime juice, and lime zest in a saucepan. Let it come up to a bubble and thicken over medium heat.
Step 2: Strain the thickened curd in a fine mesh strainer to remove any cooked eggs and most of the lemon zest.
Step 3: Add the butter and food coloring to the curd. Stir until the curd is completely green. Adjust the color to your liking. Yellow will make it brighter.
Step 4: Place plastic wrap on top of the bowl and gently press down until it's touching the curd. Place in the fridge and chill.
Step 5: Cream the butter and sugar together until light and fluff.
Step 6: Add in the egg whites and whip until light and fluffy.
Step 7: On low speed, beat the vanilla, lime zest, food coloring, yogurt, milk, and lime juice into the mixture.
Step 8: Add the salt, baking powder, and flour to the wet ingredients and mix until the flour is just incorporated.
Fill the cupcake liners half to two-thirds full. Place in the preheated oven and bake until a toothpick comes out clean or with moist crumbs.
TIP: Once the cupcakes are baked and cooled, you can use an apple corer to remove the center of the cupcakes easily. Be sure to not go all the way down to the bottom of the cupcake otherwise, the lime curd will fall out of the bottom of the cupcake when it's unwrapped.
Fill the cupcakes with lime curd, and be careful to leave some room at the top so it doesn't spill over. Pop the center of the cupcake back on or leave it off. It's up to you.
Add the frosting to a piping bag with a large round tip and pipe tall swirls on each cupcake.
These are some substitutions that I know will work without fail.
- Lime Zest/Juice - Instead of using lime in this recipe, you can use the same measurements of lemon zest/juice if you enjoy lemon more.
- Vanilla Greek Yogurt - You can use plain Greek yogurt or any flavor you want that will pair with lime or full-fat sour cream instead of the vanilla Greek Yogurt.
- American Buttercream Frosting - You can easily use your favorite frosting recipe or even store-bought that you color green.
Sharing the general equipment that I use for these slime cupcakes will hopefully help you.
- Fine Mesh Strainer with Handle - this strains the curd for the center of the cupcakes
- Cupcake Corer - an apple corer will work but it's a little smaller.
- Cupcake pan - I used a Wilton cupcake pan, but any will work.
- Piping bags - The 16-inch Wilton disposable piping bags are my go-to.
- Large round tip - I used the Wilton 2A piping tip, but you could also use a coupler.
How to Store/Freeze
Because of the lime curd filling, these will need to be stored in the refrigerator in an airtight container. If you want to keep them out at room temperature, leave the lime curd out of the center of the cupcakes until you're ready to serve them.
To freeze these lime slime cupcakes, fill them with the lime curd and top with the piece of cupcake that was cut out. Leave the frosting off so it doesn't get squished. Place the cupcakes in a freezer-safe container and store them in the freezer for up to 3 months.
To thaw the cupcakes, place them in the fridge overnight. Frost and serve!
Frequently Asked Questions
I would recommend the fresh limes just for the zest in this recipe, but I do really enjoy Nellie & Joe's Key Lime Juice that you can find in the juice section of Walmart and probably most grocery stores.
Of course not but it won't have the same Halloween feel to them.
Usually, if you stir it quite a bit it will begin to become a thinner consistency. You can also try adding a small amount of water to thin it out.
Keep cooking it! If you have a candy thermometer, let it come up to between 165 degrees F to 175 degrees F.
Looking for other Halloween dessert recipes like this? Try these:
Lime Slime Cupcakes
- 3 large eggs
- ¾ cup granulated sugar
- ¼ teaspoon salt
- ½ cup lime juice
- 1 tablespoon lime zest
- ¾ cup unsalted butter
- neon green food coloring or green and yellow food coloring
- 1 cup butter room temperature
- 1 teaspoon vanilla extract
- 1 teaspoon salt
- 4 cups powdered sugar
- 3-4 tablespoons whole milk
- Neon green food color or green and yellow food coloring
- Begin by making the lime curd since it will need to chill in the refrigerator to setup.
- In a small sauce pan, add the eggs, sugar, salt, lime juice and lime zest. Whisk until combined.
- Place over medium heat and let the curd come up to a bubble.
- As the curd begins to bubble, start stirring constantly until the mixture thickens and coats the back of a wooden spoon.
- Remove from the heat.
- Strain the hot curd with a medium sized bowl with a fine mesh strainer on top of the bowl. This will catch any cooked eggs and most of the zest.
- Add the butter and food coloring to the strained curd. Whisk until the butter has melted and the mixture is smooth.
- Cover with plastic wrap and gently press it down until it’s touching the top of the curd to prevent a skin from forming during the chill time.
- Place in the fridge and allow to chill for about an hour to set up.
- While the curd is chilling, make the cupcakes.
- Preheat the oven to 350 degrees F and line each cavity in your cupcake pans with paper liners. Set aside.
- In a large bowl, add the butter and granulated sugar. Beat with a hand mixer on medium speed until creamed, about 2 minutes.
- Add the egg whites and continue to mix on medium speed for another 2 minutes or until light and fluffy. Scrape down the bowl.
- Add the vanilla, lime zest, food coloring, yogurt, milk and lime juice. Mix on low speed until combined. Scrape the sides of the bowl.
- Add the salt, baking powder, and flour to the wet ingredients. Beat on low speed for about a minute until most of the flour is combined and then turn the mixer up to medium and beat until thoroughly combined. Stop and scrape the sides if needed and mix in any remaining bits.
- Fill each cupcake liner ⅔ full of cake batter.
- Place in the preheated oven and bake for 14 to 16 minutes or until a toothpick inserted in the center of one of the cupcakes in the center of the pan comes out clean or with moist crumbs. Remove from the oven and allow to cool completely before frosting them.
- In a large bowl, add the butter, salt, and vanilla extract. Beat using a hand mixer on medium speed until smooth.
- Add about half of the powdered sugar and half of the milk. Beat on low speed until combined. Add in the remaining powdered sugar and mix until smooth.
- Turn the speed to medium/high and beat an additional minute until the frosting is light and fluffy. The frosting should be a stiff pipeable consistency. Don’t add the remaining milk unless the frosting still looks dry at this point.
- Add in your food coloring and beat until there are no white streaks left in the frosting.
- Once the cupcakes have cooled and the curd has set up, it’s time to assemble.
- Scoop the frosting into a disposable piping bag or large storage bag fitted with a large round tip or just a hole cut in the end or in the corner of the storage bag.
- Place the lime curd in another disposable piping bag or large storage bag.
- Using a paring knife and cut into the center of the cupcakes at an angle. Your cupcake piece should look like an upside down cone when it comes out.
- Cut a small hole in the tip of the piping bag filled with the lime curd or in the corner of the storage bag.
- Fill in the center of the cupcake with the lime curd without overfilling.
- Gently place the piece of cupcake back on the top to cover the lime curd and give the frosting something to attach to.
- Begin piping a swirl on the outside edge of the cupcake and go around the cupcake. Then begin pulling up and spiraling inwards to cover the curd and create a swirled top. Repeat with the remaining cupcakes.
- Store the cupcakes in an airtight container in the refrigerator for up to 2 days.
- STORAGE: Store the cupcakes in the refrigerator for up to 7 days.
- FREEZING: Leave the frosting off the cupcakes, but still fill with the lime curd. Place the cupcakes in a single layer in a freezer-safe container and store in the freezer for up to 3 months.
- LIME ZEST/JUICE: The lime zest/juice can be substituted with the same amounts of lemons or even grapefruit.
- GREEK YOGURT: Any flavor Greek yogurt or even full-fat sour cream will work. The sour cream will make the cupcakes slightly less sweet.
(Nutrition facts are an estimate and not guaranteed to be accurate. Please see a registered dietitian for special diet advice.)