Preheat oven to 350F and boil a large kettle of water. Set aside for water bath.
Heat the sugar in a small saucepan over medium heat. Begin stirring once the sugar starts to melt and reduce the heat to medium-low. Continue stirring until all the sugar has melted and turns golden or amber in color.
1 cup (200g) granulated sugar
Immediately pour the sugar into a 9" cake pan and carefully swirl around to coat the bottom of the pan. Use oven mitts or pot holders as the pan gets very hot quickly with the melted sugar. Set aside to cool.
In a large mixing bowl, lightly beat the eggs. Add in the sweetened condensed milk, evaporated milk, and vanilla extract. Gently whisk until well combined.
5 large eggs, 1 can (14oz) sweetened condensed milk, 1 can (12oz) evaporated milk, 2 tsp vanilla extract
Slowly pour the mixture through a fine mesh sieve into the prepared pan. Tightly cover the pan with foil and place in a larger roasting dish.
Fill the roasting dish with hot water reaching halfway up the cake pan. Bake for 45-50 minutes or until a toothpick inserted into the center comes out clean. The center will be jiggly but will firm up as it cools.
Carefully remove from the hot water bath and let cool completely uncovered. Re-cover and chill in the fridge for a minimum of 4 hours or overnight.
When ready to serve, run a thin knife along the edge. Place a serving plate face-down on top and quickly flip the pan along with the plate over together. Slowly lift the cake pan to release the flan and pour all the caramel over top.
Notes
Leftovers can be wrapped in saran wrap or placed in an airtight container and stored in the fridge for up to 5 days from the day it was made.