Heat 1 cup sugar in a saucepan over medium heat until melted and golden brown
Pour the caramel into a flan mold or baking dish and tilt to coat the bottom evenly
Let the caramel cool and harden
Preheat the oven to 350°F
Whisk 4 eggs, 1 can sweetened condensed milk, 1 can evaporated milk, 1 teaspoon vanilla extract, and a pinch of salt until smooth
Strain the mixture for a smoother texture
Pour the custard over the hardened caramel
Place the mold in a larger baking pan
Add hot water to the larger pan until it reaches halfway up the sides of the mold
Bake for 50 to 60 minutes, or until the center is just set
Remove from the oven and let cool to room temperature
Refrigerate for at least 4 hours or overnight
Run a knife around the edges and invert onto a serving plate