Preheat the broiler and position the rack nearest the heat. Peel the cardboard carton off the ice cream and cut the ice cream into 4 round slices. Pack the slices into four 6-ounce ramekins, transfer to a baking sheet and place in the freezer.

In a large nonstick skillet, melt the butter. Add the diced pineapple and cook over high heat, stirring occasionally, until lightly browned, about 2 minutes. Add 2 tablespoons of the dulce de leche and cook, stirring, until the pineapple is lightly caramelized, about 3 minutes. Add the remaining 1 tablespoon of dulce de leche and transfer the pineapple to a plate. Place the plate in the freezer to cool the pineapple.

Put the egg white in a clean mixing bowl set over a saucepan of boiling water and, using an electric mixer with clean beaters, beat the egg white and salt at high speed until firm peaks form. Gradually add the sugar, 1 tablespoon at a time, and beat until the meringue is stiff and glossy.

Spoon the cooled pineapple over the ice cream along with any juices. Dollop the meringue over the pineapple and broil just until lightly toasted, about 45 seconds. Serve right away.