Cakes will have the best results if made with room temperature ingredients. I like to pull my butter, eggs, buttermilk, and sour cream out of the fridge an hour or two before I start baking.
Sprinkles: Avoid using sprinkles that will bleed into your batter. Rainbow jimmies are my favorite and the best to use for this cake. Steer clear from nonpareils, which are the little balls.
Make Ahead Instructions: The frosting can easily be made ahead of time and stored in the fridge in a sealed container. Remove frosting from the fridge an hour before you’re ready to frost the cake, to give it time to come to room temperature.
Freezing Instructions: After baking the cake layers, allow them to cool completely, then wrap them well in plastic wrap and stick each layer in a ziplock freezer bag. They can be frozen for a few months. I usually just pull them out of the freezer once I am starting to make my frosting, or an hour or two before I want to assemble.
I have given both cups and grams as measurements. Grams will be more precise, especially when measuring flour. If you don’t have a kitchen scale, no problem! Just lightly spoon flour into your measuring cup to insure its not packed in there. Light and fluffy is the key.