This cake should not be assembled until just before serving.
Ingredients
4 large egg whites
1/4 teaspoon cream of tartar
1 cup sugar
1 pound fresh rhubarb, trimmed and cut into 1/2-inch pieces (3 cups total)
1/2 cup sugar
1 tablespoon water
2 teaspoons cornstarch
1 cup well-chilled heavy cream
2 1/2 cups picked-over fresh raspberries
Accompaniment:Rhubarb Raspberry Sauce
Directions
Let egg whites stand at room temperature 1 hour.
Preheat oven to 250° F. Line 2 baking sheets with parchment paper and draw three 10- by 4 1/2-inch rectangles on parchment (2 on one sheet and 1 on other). Turn parchment over.
In a large bowl with an electric mixer beat whites with cream of tartar and a pinch salt until they hold soft peaks. Gradually add sugar, beating, and beat until meringue holds stiff, glossy peaks.
Transfer meringue to a pastry bag fitted with a 1/2-inch fluted tip and pipe evenly onto parchment rectangles, filling them in. (Alternatively, divide meringue among parchment rectangles, spreading with a spatula to fill them in.)
Bake meringue layers in upper and lower thirds of oven, switching positions halfway through baking, 1 hour, or until crisp and firm. (If weather is humid, cooking time may be longer.) Cool meringue layers completely on baking sheet in turned-off oven or on a rack and carefully peel off parchment. Meringue layers may be made 1 day ahead, wrapped well in plastic wrap or sealed in an airtight container, and stored in a cool, dry place.
In a heavy saucepan stir together purée ingredients and simmer, stirring occasionally, until rhubarb is softened, about 12 minutes. Cool mixture slightly and in a blender or food processor purée until smooth (use caution when blending hot mixtures). Transfer purée to a bowl and cool. Purée may be made 2 days ahead and chilled, covered. Bring purée to room temperature before proceeding.
Lightly whip heavy cream.
On a large platter arrange 1 meringue layer and spread evenly with 1/2 cup rhubarb purée. Spread half of whipped cream evenly over purée and top with 3/4 cup raspberries. Repeat procedure with another meringue layer, 1/2 cup purée, remaining whipped cream, and 3/4 cup raspberries. Top with remaining meringue layer.
Garnish cake with remaining cup raspberries and serve with rhubarb raspberry sauce.
