Preheat your oven to 350°F (175°C). Grease two 9-inch round cake pans with vegetable oil or butter, then line the bottom with parchment paper.

In a large mixing bowl, whisk together all-purpose flour, granulated sugar, brown sugar, baking powder, baking soda, and spices.

In another bowl, crack the eggs and whisk them gently. Add the buttermilk and vegetable oil, mixing until well incorporated.

Pour the wet ingredients into the bowl of dry ingredients, stirring gently with a spatula until just combined.

Pour the batter evenly into the prepared cake pans, using a spatula to smooth the tops.

Place the cake pans in the oven and bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.

Remove the pans from the oven and let them cool for about 10 minutes. Invert them onto wire racks to cool completely.

In a mixing bowl, beat the softened butter until creamy, then gradually add the powdered sugar, followed by the eggnog.

Once the cakes are completely cooled, frost one layer with eggnog buttercream, then layer the second cake on top and frost the entire cake.

Decorate with festive touches like cinnamon or glitter, slice, and serve.