First, prepare the caramel.
Put sugar in a saucepan over medium low heat.
Let cook until it turns brown and becomes caramel.
Immediately, pour it in a baking pan. Make sure to shake the baking pan so that the caramel coat the bottom and sides of the pan. Set aside.
In a bowl, put the eggs, salt and vanilla extract.
Add orange zest then whisk well.
Add evaporated milk, condensed milk and regular milk.
Whisk everything really well.
Pour the batter in the prepared baking pan.
Place the baking pan in a larger baking pan.
Pour hot water in the large baking pan to cover the bottom of the small baking pan.
Let cook for about 1 hour in 350°F preheated oven. The center of the flan may still giggly but no worries it will set later.
Once cooked, leave it on the counter to cool for about 1 hour then refrigerate for at least 2 hours, preferably overnight.
Run a knife around the edges of the pan to make sure that the flan will come out from the pan easily.
Gently flip the flan over a plate.
Enjoy.