Melt sugar in the pan over low heat. Spread the caramelized sugar evenly on the bottom and sides of the pan. In a bowl, beat egg yolks. Slowly add the evap milk and condensed milk to the eggs. Stir, add lime or lemon rind and vanilla. Mix. Pour mixture on pan. Place the pan on a larger shallow baking pan containing hot water about halfway up the sides of the pan with the mixture. Preheat oven to 325°F. Set pan on middle rack. Bake for 1 1/2 to 2 hours or until knife inserted on the middle comes out clean. Let it cool at room temperature. Chill and serve cold.