If using store-bought cake, skip to step 2. If making homemade cake, bake and cool your preferred sponge cake or genoise recipe in a round cake pan. Once cooled, remove from the pan and trim to fit the size of your ice cream layer. Place the cake on a baking sheet lined with parchment paper.
Line a round bowl with plastic wrap, leaving enough overhang to cover the ice cream later. Soften the ice cream slightly and spread it evenly into the bowl, creating a dome shape. Cover with the overhanging plastic wrap and freeze until firm, at least 4 hours or overnight.
In a clean, dry mixing bowl, beat the egg whites, pinch of salt and cream of tartar on medium speed until soft peaks form. Gradually add the sugar, 1 tablespoon at a time, while continuing to beat on high speed. Beat until stiff, glossy peaks form. Add vanilla extract and mix until combined.
Spread the meringue evenly over the entire dessert, ensuring it covers the ice cream and cake completely, and seals the edges. You can either spread it by hand or use a piping bag for a decorative touch.
After assembling, use a kitchen torch to carefully brown the meringue on the outside. Move the torch evenly over the surface until the meringue is lightly golden brown.
Once the meringue is nicely browned, use a sharp knife dipped in hot water to slice into portions. Serve immediately and enjoy the deliciousness!