Preheat your oven to 325°F. Prepare an 8-inch round cake pan by greasing it with butter or nonstick cooking spray. Line the bottom of the pan with parchment paper to ensure the cake releases easily after baking. Spray the bottom again for extra assurance and set aside.

In a large mixing bowl, or in a stand mixer fitted with the paddle attachment, beat the room-temperature butter and granulated sugar on medium speed until light and fluffy. This should take about 2-3 minutes. Scrape down the sides and bottom of the bowl with a rubber spatula to ensure everything is evenly mixed.

Add the eggs, one at a time, mixing well after each addition. Be sure to scrape the bowl after adding each egg to ensure even mixing. Once all the eggs are incorporated, mix in the vanilla bean paste, vanilla extract, and sour cream. Beat until the mixture is smooth and well-combined. If the mixture looks slightly curdled, don't worry—it will smooth out when you add the flour.

In a medium-sized bowl, whisk together the cake flour, baking powder, baking soda, and salt.

With the mixer on low speed, add half of the dry ingredients to the wet mixture, followed by half of the buttermilk. Mix just until combined. Repeat with the remaining flour mixture and buttermilk. Mix until the batter is smooth and no lumps remain, being careful not to overmix. Scrape down the sides and bottom of the bowl to ensure everything is fully incorporated.

Pour the batter into the prepared cake pan and use the back of a spoon or a mini offset spatula to smooth the top evenly.

Bake the cake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center of the cake comes out clean. If your oven runs hot, start checking for doneness around 30 minutes to prevent overbaking.

Once baked, remove the cake from the oven and let it cool in the pan for 10 minutes. Carefully turn the cake out onto a wire rack and let it cool completely, which will take about 40 minutes. Ensure the cake is fully cooled before frosting to prevent the frosting from melting.

While the cake cools, prepare the frosting. In a large mixing bowl, beat the room-temperature butter and cream cheese together on medium speed until smooth and creamy, about 2 minutes. Scrape down the sides and bottom of the bowl to ensure an even texture.

Once the cake is completely cool, use a serrated knife to slice the single layer horizontally into two even layers. Place the bottom layer on your serving plate or cake stand.

Spread half of the frosting over the bottom layer using an offset spatula or butter knife to create an even layer of frosting. Gently place the top cake layer on top of the frosted layer.

Spread the remaining frosting evenly over the top of the cake, leaving the sides unfrosted for a rustic, minimalist look. For a festive touch, add rainbow sprinkles or fruit on top.

Slice the cake into pieces and serve. Store leftovers in an airtight container in the refrigerator for up to 3 days. Allow the cake to come to room temperature before serving for the best flavor and texture. Enjoy!