Make ahead: Bake cake layers and prepare frosting up to one day in advance. Store unfrosted cakes covered at room temperature and keep frosting refrigerated. Bring frosting to room temperature and re-whip or thin with a splash of cream before using., Freezing: Cake layers (frosted or unfrosted) freeze well for up to 2 months. Wrap layers tightly in plastic wrap and foil. Freeze frosted cakes on a tray until firm, then wrap. Thaw in the refrigerator overnight and bring to room temperature before serving., Cake pans: Recommended 8-inch round pans for tall layers. Using 9-inch pans yields thinner layers., Blueberries: Use fresh rather than frozen to avoid extra moisture that can lead to dense cake. Toss berries with flour before folding to prevent sinking., Substitutions: Buttermilk can be replaced with whole milk due to acidity from lemon juice and brown sugar. For dairy-free adaptations, use nondairy milk, vegan butter, and dairy-free cream cheese; texture will vary., Topping variations: Add lemon curd between layers, stir in poppy seeds, or try stabilized whipped cream or mascarpone whipped cream for frosting alternative., Smart tweaks: Swapping half the butter for oil keeps the cake moist and light; the addition of baking soda with baking powder helps the cake rise better., Egg temperature: Use room temperature eggs for better mixing and texture. Warm eggs in water for 5 minutes if needed., Cream cheese frosting: Use full-fat brick-style cream cheese, not spreadable style, and ensure both cream cheese and butter are room temperature for smooth frosting.