Unfrosted butter cakes and ones iced with buttercream frosting freeze well. Place individual cake layers on a baking sheet and freeze. Once frozen, place in heavy-duty resealable plastic freezer bags. Unfrosted butter cakes can be frozen for up to 4 months; frosted butter cakes, up to 2 months. (Not all frostings freeze well.) Thaw cakes in the refrigerator.