Preheat the oven to 350 degrees F. Grease an 18x13x1 baking sheet tray with nonstick cooking spray.

In a medium bowl, add the flour, baking soda, pumpkin pie spice, cinnamon, salt, and nutmeg. Whisk until well combined.

In a large bowl, add the pumpkin puree, brown sugar, white sugar, oil, eggs, and vanilla. Whisk until the eggs are well combined.

Add the dry ingredients to the wet and stir until combined.

Pour the cake batter into the prepared baking sheet tray and spread out evenly.

Place in the preheated oven and bake for 18-20 minutes until a toothpick inserted into the center comes out clean. Let it cool slightly while you make the frosting.

Place the butter in a small saucepot over medium-low heat and let it melt. Stir occasionally.

Once melted, add the brown sugar and heavy cream. Whisk constantly until the mixture comes up to a boil. Once it comes up to a boil that can’t be stirred away, remove from the heat and whisk in the powdered sugar a little at a time until fully mixed in.

Whisk in the bourbon, if you’re using it, and vanilla.

Add the pecans and salt. Stir until combined.

Immediately pour the frosting over the warm cake. It should go right to the edge without overflowing, but if it looks like it may overflow, do not use it all. Be careful while pouring, do it slowly and evenly over the entire cake. Don’t just dump it all on top.

Allow the frosting to set fully, about 1 hour. Slice and serve.