There are many different types of frostings, icings, and glazes you can use to finish your butter cake, and a vanilla buttercream is a common and delicious choice. To make this frosting:  Place 1 cup (225 g) of softened butter in a mixing bowl or the bowl of a stand mixer. Beat on medium for about three minutes. Working in 1/2-cup increments, add 3 to 4 cups (345 to 460 g) of confectioner’s sugar (add closer to 4 cups for a firmer icing). When all the sugar has been incorporated, turn the beaters to high and mix for 10 seconds. Add a pinch of salt and 2 teaspoons (12 ml) vanilla. Beat until incorporated. Beat in 2 to 3 tablespoons (30 to 45 ml) of milk or cream until the frosting reaches the desired consistency. This is a variation on a basic buttercream, but the brown butter adds a richness and nuttiness to the frosting. To make this frosting:  On medium heat, melt 6 tablespoons unsalted butter (85 g) in a small saucepan. Stir constantly until the butter foams, bubbles, and turns a golden color. This will take about four to six minutes. Remove from the heat and cool to room temperature. In a mixing bowl, add butter, 3 cups (345 g) confectioner’s sugar, and 1 ½ teaspoons (9 ml) vanilla. Beat on medium speed, and slowly add 3 to 4 tablespoons (45 to 60 ml) milk until you achieve the desired consistency. Chocolate is another great frosting type for a butter cake, and can add another dimension to the vanilla flavor of the cake. This recipe is similar to a vanilla buttercream, but you add chocolate and malted milk powder to the mix and use less vanilla.  In a mixing bowl, add ½ cup (115 g) softened unsalted butter and 1 teaspoon (6 ml) vanilla. Mix on low to combine. Continue mixing, and gradually add in 2 cups (230 g) confectioner’s sugar, ½ cup (59 g) cocoa powder, ½ cup (65 g) malted milk powder, and a pinch of salt. One tablespoon (15 ml) at a time, add in 7 tablespoons (105 ml) of milk until the frosting is smooth, light, and spreadable. Citrus glazes also work well with butter cakes, and they are less rich than a buttercream frosting. You can use any citrus you want, or a combination, including orange, lemon, lime, grapefruit, or any other citrus you prefer. For the glaze: In a medium bowl, whisk or beat together 1 cup (115 g) confectioner’s sugar, ¼ teaspoon (the zest from a small wedge) orange zest (grated), and 1 tablespoon (15 ml) of juice from a freshly squeezed orange. Whisk until all the ingredients are incorporated and you have a smooth icing.
Make a basic vanilla buttercream frosting. Try a brown butter frosting. Indulge with a malted chocolate buttercream frosting. Go for an orange glaze.