1. Make the Baked Alaska and turn it out on a double thickness of wax paper about 22 inches long. Remove the wax-paper lining from the top of the cake and let the cake cool to room temperature before filling and rolling it.
2. For the filling, beat the chilled cream with a large whisk or rotary or electric beater until it thickens lightly, then pour in the sugar and continue to beat until the cream is stiff enough to form firm peaks on the beater when it is lifted out of the bowl.
3. With a rubber spatula, fold into it the thoroughly drained pineapple, and spread the mixture out evenly on top of the cake.
4. Roll it up like a jelly roll and either serve at once or refrigerate, covered with a sheet of foil. Just before serving, sprinkle the exposed surface of the roll with the confectioners' sugar.
