Preheat your oven to 350°F (175°C).
In a saucepan over medium-low heat, melt the sugar until it becomes a golden caramel. Pour into a baking dish and let it harden.
In a blender, combine the sweetened condensed milk, evaporated milk, eggs, and vanilla extract. Blend until smooth.
Pour the mixture over the hardened caramel in the baking dish.
Place the baking dish in a larger pan filled with hot water, creating a water bath.
Bake for about 60 minutes, or until a knife inserted in the center comes out clean.
Let it cool, then refrigerate for at least 4 hours before serving.
To serve, run a knife around the edges and invert onto a plate.