To prepare the frosting, in a medium bowl, beat the powdered sugar, cream cheese, butter, lemon zest, and lemon juice with electric mixer at low speed until combined, then increase the speed to medium for another 2 minutes, until the frosting is free of lumps. (If using a standing mixer, use the paddle attachment.) The frosting can be kept refrigerated, tightly covered, for up 2 days; whisk to smooth before using.
Recipe printed with permission by Marisa Churchill from her book Sweet & Skinny (Clarkson Potter, 2011)