Double-line a 7-inch diameter bowl large enough to hold all of the ice cream with plastic wrap, leaving a generous overhang. Let ice cream soften slightly. Pack ice cream tightly in the bowl. Cover exposed ice cream with the plastic overhang. Return bowl to freezer until it hardens.
Immediately before serving, beat egg whites until foamy. Add tartar and whip until stiff. Gently fold in powdered sugar a little at a time.
Place frozen layer cake on a stoneware plate slightly larger than the cake (this plate will go in the oven). Unwrap the top of the ice cream bowl, and place the bowl upside down, centered on the cake. Remove the bowl, and peel the rest of the plastic away from the ice cream dome. Discard plastic. Frost cake and ice cream with meringue, covering completely.
Bake in a preheated 450-degree oven for 6Ã¢ÂÂ7 minutes until meringue peaks are golden. Serve immediately with sauces and toppings on the side.