Preheat oven to 350°F (177°C). Grease and lightly flour three 9-inch cake pans.
In a large bowl using a hand-held mixer or stand mixer fitted with a whisk or paddle attachment, beat the butter on medium speed until creamy, about 2 minutes.
Place 1 cake layer on your cake stand, cake turntable, or serving plate. Spread frosting evenly on top.
Top with 2nd cake layer and evenly cover the top with more frosting.
Top with the third cake layer and evenly cover the top with more frosting. Cover the sides with a crumb coat finish of frosting.
Decorate cake with the ombre effect and follow the instructions above.
Refrigerate the cake for 2-3 hours or up to 1 day before slicing and serving. If chilling for more than a few hours, loosely cover with plastic wrap after 1 hour of refrigeration (the frosting will "set" after about 1 hour and the plastic wrap won't really ruin your frosting at that point).
Cover and store leftover cake in the refrigerator for up to 1 week.