In a saucepan over medium-low heat, melt the sugar until it becomes a golden caramel. Pour the caramel into a baking dish, tilting to coat the bottom evenly.
In a blender, combine the sweetened condensed milk, evaporated milk, eggs, and vanilla extract. Blend until smooth.
Pour the milk mixture over the caramel in the baking dish.
Place the baking dish in a larger pan filled with hot water to create a water bath. Bake in the preheated oven for about 60 minutes, or until the flan is set.
Allow the flan to cool, then refrigerate for at least 4 hours before serving. To serve, run a knife around the edges and invert onto a plate.
Notes:
Make sure to let the flan cool completely before refrigerating to avoid condensation.