Preheat oven to 400 degrees F. Spray 4 (6-ounce) ramekins with butter flavored cooking spray. Lightly coat inside of ramekins with sugar; set aside.
Place egg whites in a medium bowl. Use an electric mixer to beat egg whites to stiff, but not dry, peaks.
Stir 1/4 of egg whites into bowl with lime mixture. Spoon mixture over bowl with egg whites and gently fold together until just combined.
Divide among ramekins. Place on baking sheet and bake in preheated oven for 20 minutes or until risen and golden brown.
Serve immediately garnished with a dusting of powdered sugar and half of a sugared lime slice.