I have adapted this recipe from the Whimsical Bakehouse Book, by Kaye and Liv Hansen. The butter adds to the creaminess and lemon juice helps keep it from being too sweet, which is what citrus will do.
FROSTING, ICING, ETC RECIPE HELP

INGREDIENTS
1/2 cup (1 stick or 8 tablespoons) unsalted or salted butter
9 ounces (three 3-ounce packages) cream cheese; preferably Philadelphia Brand
6 cups powdered sugar, sifted; measure and then, sift
2 teaspoons fresh lemon juice
1 teaspoon pure vanilla extract

INSTRUCTIONS
With a stand mixer fitted with a paddle attachment, beat the butter on medium high speed until creamy. Add the cream cheese and beat on low until combined.

With the mixer on low, add 1 cup powdered sugar, and then, the lemon juice and vanilla extract. Continue to add in the powdered sugar, with the mixer on medium-low,
until the frosting becomes smooth, light and fluffy.

SARAH SAYS: Do NOT overbeat. If the frosting is too thick, add in drops of milk or cream to correct. If too thin, add in more powdered sugar or cold cream cheese.

STORAGE
Cream cheese frosting is perishable. Store, well-covered for a few days in the refrigerator.