Heat the oven to 325°F (165°C). Set a 7-inch round, 2-inch-deep metal cake pan next to the stove. In a small saucepan combine the sugar and water. Heat without stirring until deep amber, about 6–9 minutes. Carefully pour into the cake pan and tilt to coat the base. Hot caramel can burn; use mitts and keep hands clear.

Whisk yolks gently until smooth. Stir in condensed milk, evaporated milk and vanilla without beating in air. Strain into the caramel-lined pan, then cover with foil.

Set the pan inside a larger roasting pan. Add hot water to the outer pan to halfway up the custard pan. Bake for 40–55 minutes, until the edges are set, the center trembles together and it measures at least 160°F (71°C).

Lift the custard from the water bath. Cool briefly, then refrigerate within 2 hours and chill at least 4 hours. Loosen the edge with a thin knife. Invert onto a rimmed plate and let the caramel flow over the top.