Pour 1 cup of boiling water over gelatin in a medium bowl, stir to dissolve. Then stir in the pineapple-orange juice. Refrigerate about 2 hours until the mixture begins to set.

In a medium bowl, with your electric beater on high speed, beat the egg whites with the cream of tartar, until soft peaks from when the beater is slowly raised.

Now, using the rubber scraper, gently fold the egg whites into the slightly jelled fruit mixture. Do this till well combined. Then pour the mixture into the 1-quart mold. Refrigerate from 1 to 2 hours, until it is firm.

When ready to unmold, you should loosen the edge of the mold with the spatula. Invert the mold on the serving platter. Place a hot, damp dishcloth over the mold, and shake it gently to release it. You can repeat this step if you need to. Then, garnish the edge of the mold with orange slices.