Preheat the oven to 350℉ Line a 12-cup cupcake pan with cupcake liners. Set aside.
In a medium bowl, sift the flour, baking powder, baking soda, salt, cinnamon, and nutmeg. Set aside.
1 3/4 cups All-purpose flour, 1 tsp Baking powder, 1/2 tsp Baking soda, 1/2 tsp Salt, 1 tsp Ground cinnamon, 1/4 tsp Ground nutmeg
Using a mixer, beat the butter, oil, and sugar on high speed for 2 minutes. It will become pale in color.
1/2 cup Unsalted butter, 1/4 cup Oil, 3/4 cup White granulated sugar
Add in vanilla, sour cream, and eggs. Mix on medium speed until combined. Use a baking rubber spatula to scrape the bowl.
1 tsp Pure vanilla extract, 1/4 cup Sour cream, 2 Large eggs
Add in half of the dry ingredients and half of the buttermilk and mix on low speed until just combined. Repeat with the rest of the dry ingredients and buttermilk. Take off the mixer and use the spatula to mix everything together.
1/2 cup Buttermilk
Spoon 1 Tablespoon of batter into the pan. Sprinkle a heaping 1/2 Tablespoon of cinnamon filling on top. Add another tablespoon of batter. Add another 1/2 tablespoon of cinnamon filling. Use a butter knife to swirl the top of the filling into the cupcake batter.
Bake for 17-22 minutes. Bake until a toothpick inserted comes out clean.
Let the cupcakes sit in the hot pan for 10 minutes before transferring to a cooling rack. Cool the cupcakes completely before decorating.