Preheat oven to 325°F. Add sugar to a heavy-duty saucepan over medium-low heat, stirring continuously 4-6 minutes or until melted into a golden-brown caramel. Quickly pour into a deep pie dish before caramel sets, swirling it around to coat the bottom and sides.
Mix together the evaporated milk, condensed milk, eggs and vanilla in a medium bowl. Pour mixture into the pie dish, and place it in a large roasting pan. Fill the roasting pan with about 1 inch of warm water.
Bake 45-50 minutes, or until a knife inserted in the center comes out clean. Remove flan from the roasting pan and cool. Refrigerate 4 hours or overnight.
To serve, run a spatula around the edge of the pie dish. Put a large serving plate upside down over the flan and flip it all over to release the flan onto the plate. Garnish with vanilla beans if desired.
Servings 8