Preheat the oven to 425 degrees.
In a 2-quart saucepan, combine the apples and water. Bring to a boil over high heat. Reduce the heat to low, cover, and simmer, stirring occasionally, for 10 minutes, or until the apples are tender. Stir in the sugar substitute and almond extract. Remove from the heat and place in the refrigerator for 10 minutes. (Place a hot pad underneath the pot in the refrigerator.)
In a large bowl, with an electric mixer on high speed, beat the egg whites until stiff peaks form. (You can test this by detaching the whisk attachment and holding it up. If the egg whites curl over and form a firm hook, you're done.)
With a rubber spatula, gently fold the whites into the cooled apple mixture. Spoon the mixture into a 1 ½-quart soufflé dish.
Bake for 15 minutes, or until the soufflé is puffed and browned.
Sprinkle with the almonds before serving, if using. Serve warm.