Cut the pound cake into eight 3/4-inch-thick slices. Cut a circle from each slice using a 4- or 6-ounce ramekin as a guide; crumble the scraps. Fit each piece of cake in a ramekin, then fill with the ice cream to about 1/4 inch from the top. Sprinkle with the cake crumbs. Freeze until the ice cream is hard, at least 1 hour.
Combine the egg whites, sugar and cream of tartar in a bowl and place over a saucepan of simmering water. Whisk over low heat until the sugar is dissolved and the egg whites are warm, about 5 minutes. Remove the bowl from the saucepan and beat the whites with a mixer on high speed until they hold stiff peaks. Transfer the meringue to a pastry bag with a round tip and pipe on top of the ice cream and cake crumbs to completely cover. Make a small indent, about 1 inch deep, in the top of the meringue, for the rum.
Brown the meringue all over (including the indentation) with a kitchen torch. Place the rum in a small pot over low heat until warm but not boiling. Transfer to a liquid measuring cup and pour into the indentation in each dessert. Light the rum with a match. Let the flame burn out and serve immediately.
Photograph by Levi Brown
Recipe courtesy Brian Boitano for Food Network Magazine