- Nonstick vegetable oil spray
- 1/2 cup all purpose flour
- 2 tablespoons sugar
- 2 tablespoons (1/4 stick) unsalted butter, melted
- 1/4 cup sugar
- 1 1/2 tablespoons all purpose flour
- 1/2 teaspoon baking powder
- 1/4 teaspoon salt
- 3 large egg whites
- 1 large egg
- 2 tablespoons fresh lemon juice
- 2 tablespoons fresh orange juice
- 2 tablespoons fresh lime juice
- 3/4 teaspoon grated lemon peel
- 3/4 teaspoon grated orange peel
- 3/4 teaspoon grated lime peel
- 2 large egg whites
- 1/8 teaspoon cream of tartar
- 2 tablespoons sugar
- 1/4 teaspoon grated lemon peel
- 1/4 teaspoon grated orange peel
- 1/4 teaspoon grated lime peel
- Preheat oven to 350°F. Spray 8x8x2-inch metal baking pan with nonstick vegetable oil spray. Mix flour and sugar in large bowl. Add melted butter and stir with fork until mixture forms coarse crumbs (mixture will be dry). Using fingers, press crumbs over bottom of prepared baking pan. Bake until crust is set and light golden, about 20 minutes. Cool crust completely on rack. Maintain oven temperature.
- Mix first 4 ingredients in small bowl. Whisk egg whites, egg, juices and peels in medium bowl. Add flour mixture; whisk until smooth. Pour filling over crust.
- Bake tart until filling is set, about 18 minutes. Cool completely on rack. (Can be made 1 day ahead. Cover and chill.)
- Preheat oven to 350°F. Beat egg whites and cream of tartar in clean large bowl until soft peaks form. Add sugar 1 tablespoon at a time and beat until stiff peaks form. Spoon meringue over filling, covering completely. Sprinkle peels atop meringue. Bake until meringue tips begin to brown, about 10 minutes. Transfer to rack. Cool completely. Cut into 6 pieces.