01 - Preheat oven to 350°F. Line a 9x5-inch loaf pan with parchment paper, leaving overhang to aid removal.
02 - Cream butter and sugar until light and fluffy. Beat in eggs one at a time, then stir in vanilla extract.
03 - Whisk flour, baking powder, and salt in a separate bowl. Alternate adding dry ingredients and milk to wet mixture, mixing until just combined.
04 - Pour batter evenly into prepared pan. Bake 20-22 minutes, or until a toothpick inserted in center comes out clean. Cool completely in pan.
05 - Remove cooled cake from pan. Clean and re-line pan with fresh parchment. Place cake back into the pan.
06 - Spread softened vanilla ice cream evenly over cake. Smooth surface, cover with plastic wrap, and freeze at least 4 hours until firm.
07 - Beat egg whites with cream of tartar until soft peaks form. Gradually add sugar and beat until stiff, glossy peaks form. Fold in vanilla extract.
08 - Lift cake and ice cream from pan using parchment overhang. Invert onto a parchment-lined baking sheet. Spread meringue evenly over top and sides, sealing edges.
09 - Preheat oven to 500°F or set broiler to high. Bake 2-3 minutes, watching closely until golden, or use kitchen torch to brown meringue.
10 - Slice to serve immediately or return to freezer until needed.