Preheat your oven to 175°C (350°F). Heat the sugar in a saucepan over medium heat, stirring until it melts and turns golden brown. Quickly pour the caramel into the bottom of a round baking dish or ramekins, tilting to coat the bottom evenly.

In a bowl, whisk together eggs, sweetened condensed milk, evaporated milk, and vanilla extract until smooth. Pour the mixture over the caramel layer in the baking dish.

Place the dish in a larger baking pan and add hot water to the pan to create a water bath. Bake for 50 minutes, or until the custard is set but still slightly jiggly in the center.

Remove the flan from the oven and let it cool to room temperature. Refrigerate for at least 2 hours before serving. To unmold, run a knife around the edges and invert onto a plate.