Raspberry liqueur in the recipe brings a light, fruity flavor to these cupcakes crowned with a crisp meringue topping.
Preheat oven to 350 degrees F. Line twelve 2-1/2-inch muffin cups with paper bake cups or lightly coat muffin cups with nonstick spray for baking; set pan aside.
In a small bowl, stir together flour, baking powder, and salt; set aside. In a large bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add the 3/4 cup sugar. Beat on medium to high speed for 1 minute. Add egg, egg yolks, raspberry liqueur, and vanilla; beat until combined. Alternately add flour mixture and milk to butter mixture, beating on low speed after each addition just until combined.
Spoon batter into the prepared muffin cups, filling each about three-fourths full. Bake for 15 minutes. Meanwhile, wash beaters thoroughly.
In a medium bowl, combine egg whites and cream of tartar. Beat on medium speed until soft peaks form (tips curl). Gradually add the 2/3 cup sugar, 1 tablespoon at a time, beating on high speed until stiff peaks form (tips stand straight).
Pipe or spoon meringue on top of cupcakes. If desired, place a raspberry on top of each cupcake, pressing into meringue. Bake for 8 to 10 minutes more or until meringue is lightly browned.
Cool cupcakes in pan on a wire rack for 5 minutes. Remove from pan; cool slightly. Serve warm. (Or cover loosely and chill for up to 4 hours before serving.) Makes 12 cupcakes.