Layers of hazelnut-and-chocolate meringue meld with refreshing raspberry sorbet. This cake should be made the day before serving.
Preheat oven to 350 degrees F. Line two 18-by-12-inch baking sheets with parchment paper. Draw 3 circles on the paper using an 8-inch cake pan or plate as a guide. Turn the paper over; the lines will show through. (Alternatively, line two baking sheets with aluminum foil, lightly coat with nonstick cooking spray and dust with flour, shaking off excess. Trace the circles onto the foil with your fingertip.)
Spread hazelnuts in a pie plate and bake until lightly toasted and fragrant, 8 to 12 minutes. If hazelnuts have skins, place them on a clean kitchen towel, fold the towel over and rub off as much skin as you can. Let cool. Reduce the oven temperature to 250 degrees F.
Place the toasted hazelnuts, confectioners' sugar, cocoa and cornstarch in a food processor; process until the nuts are ground.
Beat egg whites and cream of tartar on low speed in the bowl of an electric mixer until frothy. Gradually increase the mixer speed to high. When the whites begin to form soft peaks, decrease the speed to medium and slowly beat in sugar, 1 tablespoon at a time. Add vanilla; continue beating until the meringue is glossy and stiff peaks form. Sprinkle the reserved hazelnut-cocoa mixture over the meringue and fold in with a large rubber spatula just until mixed.
Spoon the meringue into a piping bag fitted with a 1/2-inch open-star tip. Pipe a layer of meringue in a tight spiral to fill each circle on the prepared baking sheet. (Alternatively, spread the meringue onto the circles with a spatula.)
Bake the meringue layers until golden and firm to the touch, 50 to 70 minutes. Let cool on baking sheets on racks, then carefully peel off the paper or foil.
Let sorbet soften in the refrigerator for about 30 minutes. Carefully trim the meringue layers to fit snugly into an 8-inch springform pan. Set a meringue layer in the bottom of the pan and spread half of the sorbet evenly over the meringue. Set the second meringue layer on top of the sorbet. Cover with the remaining sorbet and the third meringue layer. Cover the torte with plastic wrap and freeze overnight or for up to 5 days.
Before serving, let the torte soften in the refrigerator for about 30 minutes. Run a sharp knife around the edge of the pan to loosen the cake. Transfer to a cake plate and dust with confectioners' sugar. Garnish with fresh raspberries.
Make Ahead Tip: Torte will keep, wrapped, in the freezer for up to 5 days. Let soften in the refrigerator for 30 minutes before serving.
3 other carbohydrate, 1 fat