Flan de Leche

Make the caramel

1. Pour the sugar into a flanera or cake pan or, if using ramekins, a large saucepan. Place the pan over medium heat and move the pan constantly, without stirring, until the sugar melts and takes on a deep amber hue, 4 to 8 minutes.
2. Remove the pan from the heat and tilt the pan so that the bottom and sides are lightly covered with the caramel. The caramel will be very hot and should be handled carefully. If using ramekins, immediately and carefully divvy the caramel among the ramekins. Set the pan or ramekins aside.

Make the custard

1. Combine the whole milk, evaporated milk, sugar, cinnamon stick, vanilla bean or extract, lemon zest, and salt in a heavy 4-quart saucepan and bring to a boil over medium heat. Remove the saucepan from the heat and let steep until the milk has cooled to room temperature, about 30 minutes.
2. Preheat the oven to 350ºF (177°C).
3. Remove and discard the cinnamon stick, vanilla bean (if using), and lemon zest from the milk mixture. Combine the cooled milk mixture and eggs in a bowl and whisk until well combined. Carefully pour the custard into the prepared pan or ramekins, straining it if desired. Close the lid of the flanera, if using, or tightly cover the pan or ramekins with aluminum foil.
4. Place the filled pan or ramekins inside a larger roasting pan. Pour enough hot water into the roasting pan so that it comes about halfway up the sides of the flanera or ramekins. Carefully transfer the roasting pan to the oven and bake for 60 to 75 minutes, until a knife inserted into the center of the flan comes out clean.
5. Let the flan cool completely at room temperature, then loosely cover and refrigerate for at least 4 hours or overnight.
6. To unmold the flan, run a thin knife around the edge of the pan. Gently shake the pan to loosen the flan. Place a large plate over the flan and quickly invert the pan in one motion. The flan will gently drop onto the plate and a generous amount of caramel will spill out and pool around the flan. Serve at once.