Make Caramel. Add sugar to a saucepan, heat over medium-low. Allow the sugar to dissolve in a few minutes. Increase the heat to medium high. Cook the sugar to caramelize by stirring until it turns honey color.
Remove from the heat and immediately pour the hot caramel into the bottoms of the round pan, quickly and carefully tilt the pan to coat the bottom evenly. Set aside to let the caramel harden.
Make Custard. Preheat oven to 350°F/175°C.
Combine heavy cream, whole milk, condensed milk and salt in a heavy bottomed saucepan and bring to a simmer over medium heat. Do not bring it to boil. Remove the pan from the heat. Set aside.
In a large bowl, whisk the eggs, egg yolks and vanilla extract until combined. Slowly add the hot milk mixture to the eggs mixture while whisking the egg mixture constantly to prevent curdling. Strain the mixture into a large bowl to remove bits of curdled eggs then transfer strained custard into the prepared round pan with caramel at the bottom.
Place the round pan in the center of a baking or roasting pan and pour in boiling water until it reaches halfway up the sides of round pan. Bake for 45-55 minutes until custard has set at the edges but still slightly jiggly in the center when you gently shake. Remove the pan from baking/roasting pan and allow it to cool to room temperature, then chill in the refrigerator for at least 4 hours, preferably overnight.
To remove flan from pan. Run a sharp knife around the edges of the pan. Flip a large rimmed serving platter over the round pan, and quickly invert the custard on the platter. If it doesn’t come out, gently shake the pan from side to side a few times to remove it. Caramel flan is best served cold. Leftovers can be refrigerated up to 5 days.