Before you begin, make sure your butter and cream cheese are at room temperature. Place them in the bowl of your stand mixer with vanilla and a pinch of salt. Beat on low speed until smooth. If you see little lumps of cream cheese, just keep mixing until they disappear.

Add the powdered sugar and a spoonful of sour cream, mixing until the frosting becomes thick, creamy, and silky. Stop as soon as it reaches that perfect smooth consistency.

I like to make the buttercream ahead of time so it can chill and develop its flavor. You can prepare it a few hours before or even a day in advance. Keep it covered in the fridge, then bring it to room temperature before frosting. Stir it well to make it smooth and airy again.

Once the cakes are fully cooled, trim off any domed tops with a serrated knife. For a tall, elegant four-layer cake, carefully slice each layer in half horizontally.

Place one layer, bottom side down, on a cake stand or turntable. Spread a generous layer of buttercream over the top, right to the edges. Add the next layer, and repeat until all layers are stacked, finishing with the last one bottom side up for a flat surface.

If your cake is tall, slide a dowel or skewer through the center to keep it steady. Use an offset spatula to frost the top and sides with smooth, even strokes. You can keep it simple or decorate however your heart desires.

This cake is best enjoyed the same day you assemble it. Store any leftovers in an airtight container at room temperature or in the refrigerator. It will stay fresh and tender either way.