Make the caramel: Add enough cold water to just cover the sugar in a pan. Heat over medium heat. Be patient and cook until the mixture turns a light amber color, then remove from heat (the caramel will continue to cook after you turn off the heat, so stop as soon as it reaches a light amber to avoid burning). Squeeze in a little lemon juice. Quickly pour the caramel into your molds, tilting to coat the bottom evenly. Let cool until set.

Crack the eggs into a bowl and whisk until well blended. Set aside.

In a saucepan, combine the sugar, milk, and coconut milk. Heat over medium, stirring until the sugar dissolves. Warm the mixture, but do not let it boil.

Pour the milk mixture into the eggs, whisking to combine.

Strain the mixture through a fine mesh sieve. Add the salt and vanilla extract.

Pour the mixture into the molds with the set caramel.

Place the flan molds in a large baking pan. Pour boiling water into the pan until it reaches halfway up the sides of the molds, and lay a towel on the bottom of the pan to keep the molds from sliding.

Preheat the oven to 300°F (150°C). Bake with only the lower heat for 30–35 minutes. The flan is done when the surface is set and a toothpick inserted comes out clean.