Preheat oven to 350 degrees F. Lightly grease four 1 cup ramekins with butter.
Separate egg yolks from whites. Beat egg whites until soft peaks form; set aside.
Combine 2 tablespoons butter, sugar, egg yolks, and l tablespoon lime zest. Beat on medium speed until creamy and light, about 4 minutes. Using a wooden spoon fold in flour, baking powder, salt, milk and 1/2 cup lime juice into the sugar and egg mixture. Combine well. Gently fold in the egg whites, 1/3 at a time.
Divide batter among the ramekins and bake for 30 to 40 minutes until tops are golden and the pudding has set. Serve warm.