For a two-layer cake, I double this recipe. It never hurts to have a little of this left over; you can always color it and use it for decoration.
CREAM CHEESE FROSTING
4 ounces cream cheese, at room temperature
3 tablespoons unsalted butter, at room temperature
1 1/2 cups confectioners' sugar
1/2 teaspoon vanilla extract
[juice of 1/4 lemon: I omit this unless I'm making the frosting for carrot cake]
Cream the cream cheese and butter in a standing mixer.
Slowly add the confectioners' sugar. If my sugar is at all lumpy, I sift first. To keep it from flying around, I often cover my mixer with a dish towel, which goes right into the laundry afterwards.
Stir in vanilla and lemon juice (if using).
If you need to make this ahead of time, cover and store in the refrigerator, bringing to room temperature before using.