Nutrition per serving may change if servings are adjusted.
Almond Meringue Crust
1/3 cup slivered or chopped blanched almonds
2/3 cup sugar, divided
1 1/2 tablespoons cornstarch
3 large egg whites, at room temperature
1/4 teaspoon cream of tartar
1/2 teaspoon vanilla extract
3 ripe mangoes, (3/4-1 pound each)
1 tablespoon sugar
1/2 teaspoon freshly grated lime zest
1 teaspoon unflavored gelatin
2 tablespoons lime juice
1/4 cup whipping cream
1/4 cup guava jelly, or strained apricot preserves
To make almond meringue crust: Preheat oven to 300 °F. Line a baking sheet with parchment paper. Using a 10-inch cake pan or plate as a guide, draw a circle on the paper. Turn paper over; the line will show through. (Alternatively, line the baking sheet with aluminum foil, coat with nonstick cooking spray and dust with flour, shaking off excess. Trace the circle with your fingertip.)
Spread almonds in a pie plate and bake for 8 to 15 minutes, or until lightly toasted. Let cool, then put them in a food processor along with 1/3 cup of the sugar and cornstarch; process until the nuts are coarsely ground; set aside.
Beat egg whites in a clean mixing bowl with an electric mixer at low speed for 20 seconds. Add cream of tartar and gradually increase speed to high. When the whites begin to form soft peaks, gradually add the remaining 1/3 cup sugar and vanilla; continue beating until the meringue is glossy and stiff peaks form. Sprinkle the almond-sugar mixture over the meringue and fold in with a rubber spatula just until mixed.
Spoon about 1 cup of the meringue into a piping bag fitted with a 1/2-inch open-star tip. Spread the remaining meringue inside the traced circle. Pipe the reserved meringue on the outside edge to form a rim.
Reduce oven temperature to 250 °F. Bake the meringue crust until golden and firm to the touch, 50 to 70 minutes. Let cool on the baking sheet on a rack. Carefully peel off the paper or foil
To make mousse: About 3 hours before serving, cube 1 of the mangoes and place in a food processor or blender, along with sugar. Process until smooth. To remove fibers, press the puree through a fine sieve set over a bowl. (You should have about 1/2 cup of puree.) Stir in lime zest; set aside.
Sprinkle gelatin over lime juice in a small heatproof bowl; let stand until softened, about 1 minute. Set the bowl over barely simmering water until the gelatin has melted, or microwave on high for 20 to 40 seconds. Whisk into the mango mixture. Refrigerate, stirring occasionally with a rubber spatula, until slightly thickened and beginning to set, about 20 minutes. Whip cream in a chilled bowl just until it forms soft peaks. Gently fold into the mango mixture.
To assemble tart: Melt guava jelly or apricot preserves in a small saucepan over low heat. Set the meringue crust on a serving plate. Brush a thin coat of guava jelly or apricot preserves—using about 2 tablespoons—over the crust. (Set the saucepan aside.) Spread the mango mousse inside the crust. Cover loosely and refrigerate until the mousse has set, about 2 hours. Not more than 1 hour before serving, peel and thinly slice the remaining 2 mangoes. Fan the slices on top of the mango mousse. Rewarm jelly or preserves and brush over the mangoes. Refrigerate until serving time.
Make Ahead Tip: Store the crust (Steps 1-5) in an airtight container for up to 3 days.