Preheat oven to 400°. Spray four 1-cup ramekins with cooking spray (or brush with melted butter). Add 2 tablespoons of the sugar to 1 of the ramekins and rotate it to coat with sugar. Tap the excess sugar into another ramekin and repeat until all the ramekins are coated with sugar.
In a food processor, puree bananas with lime juice, egg yolk and 2 tablespoons of sugar until smooth. Pour into a large bowl.
In a stainless steel or glass bowl, beat egg whites with a pinch of salt until soft peaks form. Add the remaining 1 tablespoon of sugar and beat until firm and glossy.
Using a rubber spatula, beat one-fourth of the beaten whites into the banana mixture, then gently fold in the remaining whites. Pour soufflé mixture into prepared ramekins and tap them lightly on a countertop.
Set ramekins on a baking sheet and bake in the center of the oven for about 15 minutes, or until golden brown and risen.