01 - Line a 9-inch bowl with plastic wrap. Pack the softened vanilla ice cream into the bowl, smooth the surface, cover with plastic wrap and freeze until firm, minimum 2 hours.
02 - Place the sponge cake on a parchment-lined baking sheet. Unmold the ice cream dome onto the cake center, then return to the freezer.
03 - Set the oven to 500°F or prepare kitchen torch for browning.
04 - Beat egg whites with cream of tartar using an electric mixer until soft peaks form. Gradually add sugar while beating until stiff, glossy peaks develop. Incorporate vanilla extract.
05 - Remove cake and ice cream from freezer. Spread meringue evenly over the ice cream and cake, ensuring all edges are sealed.
06 - Bake in preheated oven 3-5 minutes until golden brown or use a kitchen torch to brown the surface evenly.
07 - Serve immediately. Slice using a sharp knife warmed in hot water for clean cuts.