Use this recipe to make our Lemon, Blackberry, and Meringue Parfait.
Whisk egg whites, sugar, and cream of tartar in a heatproof mixing bowl set over a pan of simmering water until sugar has dissolved and whites are hot to the touch, 3 to 3 1/2 minutes.
Remove from heat. Beat on low speed, gradually increasing to high, until stiff, glossy peaks form, about 10 minutes. Beat in the vanilla. Use immediately.