1/2 cup granulated sugar
3 cups all-purpose flour
3 tablespoons melted butter
2 eggs (at room temperature), separated
3 tablespoons Key lime juice
1 teaspoon grated Key lime rind
1 cup milk (at room temperature)
Preheat oven to 325 degrees F. Grease a 1-quart baking pan or 6 custard cups.
Combine sugar, flour and melted butter in a mixing bowl. Add the unbeaten egg yolks, lime juice, lime rind and milk.
Beat egg whites until stiff; fold into yolk mixture.
Pour into pan or custard cups. Place in pan of hot water; bake 1 hour (35 minutes for custard cups), until pudding leaves sides of pan.