Swiss Meringue Buttercream
You will need 15 cups of buttercream to complete Martha's Meyer Lemon Anniversary Cake (14 cups for frosting the cake; one cup for piping around the layers and assembling the toppers).
- 8 large egg whites
- 2 1/2 cups sugar
- 1/4 teaspoon salt
- 3 cups (6 sticks) unsalted butter, cut into pieces, softened
- Yellow gel-paste food coloring
Whisk egg whites, sugar, and salt in the heatproof bowl of an electric mixer set over a pan of simmering water until sugar has dissolved and mixture registers 160 degrees, about 4 minutes. Attach bowl to mixer fitted with the whisk attachment. Beat on high speed until cool and stiff (but not dry) peaks form, about 6 minutes.
Fit mixer with the paddle attachment. With mixer on medium-low speed, add butter, several pieces at a time, mixing well after each addition (meringue will deflate slightly as butter is added). Mix until frosting comes together but is still smooth and glossy, 3 to 5 minutes. Tint with food coloring; stir until smooth.