* If you don’t have 3 23-cm/9-inch baking pans, or if three (or even two) pans don’t fit into your oven, it’s best to divide the ingredients for the cake layers and make several batches. If you let the batter for the cake layers sit for too long, it might affect the structure of the cake. It’s what I did, too!
** You can make these up to a week ahead!
*** Cakes can be made ahead. After the cakes have cooled to room temperature, remove from the pans by running a knife along the edges of the cakes to loosen them from the pans. Wrap cakes tightly in plastic wrap and refrigerate for up to 3 days, or freeze for up to 2 months. Allow frozen cakes to thaw in the fridge before use.
**** Allow buttercream that has been refrigerated to come to room temperature, then beat with a mixer fitted with the paddle attachment until smooth and creamy again.