Meringue Flowers with Lemon Curd

Make the meringue:

Heat the oven to 200°F. Whisk 4 egg whites, 1/2 cup sugar, and cream of tartar until mixture is frothy and warm to the touch in a large metal bowl set over a pot with 1 inch of simmering water -- about 3 minutes. Remove the bowl from the heat, stir in the vanilla, and beat to stiff peaks using an electric mixer on high speed. Set aside.

Shape the meringues:

Line two baking pans with parchment paper. Fill a large pastry bag fitted with a large star tip with the meringue and pipe 2-inch coiled rounds onto the prepared pans. Pipe small stars around the rim to form flowers. Bake for 1 hour in the middle rack of the oven. Do not open the oven door. Reduce the temperature to 175°F and continue to bake until meringues are hard and dry -- 35 to 45 minutes. Cool completely on the pans on wire racks. Store in an airtight, moisture-proof container up to 2 days.

Make the lemon curd:

Whisk the remaining 4 yolks, egg, lemon juice, and remaining sugar together in a heavy saucepan. Set the pan over medium low heat and stir constantly until thickened -- about 13 minutes. Remove from the heat and strain into a clean bowl. Add the butter in 4 additions, stirring between each. Cool completely and chill until ready to use. Fill the center of each meringue with 1 1/2 teaspoons of lemon curd. Garnish with fresh whipped cream, if desired.