Wash the lemons thoroughly to remove any pesticides or wax. Zest the lemons using a microplane, ensuring only the yellow outer layer is taken. Cut the lemons in half and juice them, collecting the juice in a separate bowl.

In a pot, combine water, lemon juice, and sugar. Heat over medium, stirring until sugar dissolves completely, about 5 minutes.

Once simmering, add in lemon zest. Maintain the simmer for 25-30 minutes, stirring frequently until it thickens.

To test doneness, perform the cold plate test by placing a spoonful of jam on a cold plate from the freezer. If it holds its shape, it's ready.

Carefully pour the jam into sterilized jars, leaving space at the top. Cool to room temperature for about 30 minutes before sealing and refrigerating.