Preheat oven to 335 degrees F and prepare cake pans with nonstick cooking spray and parchment circles. I used 3 7 inch round pans. On medium speed, cream together unsalted butter, granulated sugar, and brown sugar until light and fluffy.
Add in eggs one at a time, continuing to mix in between each addition.
Add in sour cream and vanilla extract. Mix until smooth. In a separate bowl, add the cake flour, baking powder, salt, cinnamon and nutmeg, and whisk to combine. On the lowest speed, add the dry ingredients to the butter mixture alternating with the buttermilk: 1/3 dry ingredients, 1/2 buttermilk, 1/3 dry ingredients, 1/2 buttermilk, and 1/3 dry ingredients.
Once all the ingredients are added and combined, scrape the sides and bottom of the bowl and mix for an additional 30 seconds. Be careful not to overmix the batter!
Pour the batter into the prepared cake pans. Use a kitchen scale to create even layers. Bake the cake for approximately 30-35 minutes. You will want to bake the cake layers until an inserted toothpick comes out clean or the cakes bounces back when gently touched.
Cool the layers in the pans for about 30 minutes and then remove to a wire cooling rack. After the cake layers are cool, level with a serrated knife.