The tangy citrus filling of this grapefruit dessert is a refreshing counterpart to the rich almond and chocolate crust. Top the fruit tart with grapefruit sections and whipped cream just before serving.
Preheat oven to 375 degrees F. Place almonds in a blender or food processor. Cover and blend or process until ground. In a small bowl stir together ground almonds and the 3 tablespoons sugar. Drizzle with melted butter; toss gently to coat. Press mixture evenly onto bottom and up side of a 9- to 9-1/2-inch tart pan that has a removable bottom. Bake about 12 minutes or until golden. Cool on a wire rack.
In a small saucepan cook and stir chopped chocolate over low heat until melted. Spread melted chocolate over bottom of crust; set aside.
For filling, in a medium saucepan heat the 1/2 cup butter over medium heat until melted. In a small bowl combine the 3/4 cup sugar and cornstarch; stir into melted butter. Stir in grapefruit peel, grapefruit juice, orange juice, and cream. Cook and stir until thickened and bubbly. Cook and stir for 2 minutes more. Remove from heat. Gradually stir about 1 cup of the hot mixture into egg yolks. Add egg yolk mixture to saucepan. Bring to a gentle boil; reduce heat. Cook and stir for 2 minutes.
Place saucepan in a large bowl of ice water and stir frequently until filling is cool. Pour filling into baked crust, spreading evenly. Cover surface with plastic wrap and chill for 3 to 4 hours or until set.
To serve, remove side of pan. Cut tart into wedges. Top each serving with whipped cream and grapefruit sections and/or cocoa powder. Makes 12 servings.