Line a 9-inch bowl with plastic wrap; press in softened ice cream. Freeze at least 4 hours until solid.

Trim cake to a 9-inch circle. Invert frozen dome onto cake; remove wrap.

Freeze assembled cake 1 hour while heating oven to 500°F.

Beat whites, cream of tartar, and salt to soft peaks. Gradually add sugar; beat stiff and glossy. Beat in vanilla.

Completely cover cake and ice cream with thick, continuous meringue. Bake 3 to 5 minutes until browned; slice immediately.