Preheat oven to 350 degrees F. Line the cupcake pan with paper liners.
In a large bowl, add the 1/2 cup butter and 1 1/4 cups granulated sugar. Beat with a hand mixer on medium speed until light and fluff, about 2 minutes.
Add in the 3 tablespoons vegetable oil and then 4 large eggs, one at a time. As soon as each egg is incorporated, scrape down the sides and bottom of the bowl and add another egg. Once all the eggs are combined, beat on medium speed for an additional 2 minutes. The batter will become thick and very pale.
Measure out the 1/2 cup buttermilk and add the 1 teaspoon vanilla extract to it. Set aside.
In a separate bowl, add the 1 3/4 cups cake flour, 1 teaspoon baking powder, 1/2 teaspoon baking soda, and 1/2 teaspoon salt. Whisk until combined.
Alternately add the dry ingredients and buttermilk mixture to the butter mixture, starting and ending with dry ingredients. Mix on medium speed until combined and scrape down the sides of the bowl after each addition.
Fill the cupcake liners about two-thirds full of batter.
Place the cupcake pan into the preheated oven and bake for 17 minutes or until the cupcakes are done. Test the center cupcakes by inserting a toothpick in the center of the cupcakes. Moist crumbs or a clean toothpick mean they're done, wet batter means they need to bake longer.
Remove from the oven and let cool completely.
Frosting
In a large bowl, add the 1 cup butter and 8 ounces cream cheese. Beat with a hand mixer on medium speed until smooth.
Add in the dry 3 ounce box peach jello, 4 cups powdered sugar, and 2 tablespoons of milk. Beat until incorporated. If it's too thick add an additional tablespoon of milk. For a fluffier frosting, beat on high for 30 seconds to 1 minute.
Add the frosting into a piping bag fit with a 1M tip.
Pipe tall swirls on top of the cupcakes.
Store cupcakes in an airtight container in the refrigerator.
Notes
Storage: Store in an airtight container in the refrigerator for up to 5 days.