Beat egg whites and salt in a small bowl until soft peaks form. Gradually add sugar 1 tbsp (15 mL) at a time and continue beating until stiff and glossy. Place cake slices on ungreased baking sheet. Top each with ice cream and quickly cover with meringue, being sure to seal edges completely. Swirl meringue into peaks. Keep in freezer until ready to bake. Freeze for at least 1 hour. Bake in a preheated 240°C (475°F) oven until meringue is lightly browned, about 2 to 4 minutes. Serve immediately.