Line a 9 inch diameter bowl with plastic wrap. Pack the ice cream into the bowl, smoothing the top with an offset spatula. Cover the bowl with plastic wrap and freeze until solid (about 8 hours).

Preheat oven to 350 degrees. Spray a 9 inch round cake pan with cooking spray. Line the pan with parchment and also spray the paper.

Whisk the flour, cocoa, and salt in a bowl to combine.

Beat the butter and sugar in a large bowl with an electric mixer until fluffy. Beat in the egg, then scrape downy the sides of the bowl. Add the dry ingredients and the buttermilk to the creamed butter and sugar, in two or three alternating additions, mixing until combined. Stir in red food coloring and vanilla.

Combine the vinegar and baking soda in a small bowl (it will bubble up). Fold into the cake batter. Pour the cake batter into the pan. Bake until the cake springs back when lightly touched, about 25 minutes. Let the cake cool for 10 minutes, then turn out onto a cooling rack to cool completely.

Beat the egg whites with an electric mixer in a large bowl until frothy. Add the cream of tartar and salt and beat until soft peaks form. Gradually beat in the sugar and beat until stiff peaks form.

If necessary, level off the top of the cake with a serrated knife. Place the cake layer on a parchment paper lined baking sheet. Remove the plastic wrap covering the bowl of ice cream and unmold the ice cream, flat side down, on the cake layer. Peel the plastic wrap off the ice cream. Cover the cake and ice cream with the meringue, making sure to reach all the way down to the parchment paper, leaving no holes. Use the back of a spoon to make peaks in the meringue. Freeze the dessert for 2 hours.

Set a rack in the center position and preheat oven to 425 degrees. Remove the dessert from the freezer and bake just until the meringue is browned, about 8 minutes. Alternatively, brown the meringue using a kitchen torch. Serve immediately.