Prepare a boiling water bath canner and four half pint jars. Place lids in a small saucepan and bring to a low simmer.
Juice the lemons and measure out 2 1/2 cups of juice. Pour it into a saucepan and add the sugar.
Stir to combine, bring to a boil and simmer for two minutes.
Funnel into the prepared jars, wipe rims, apply lids and rings, and process in a boiling water bath canner for 10 minutes.
When time is up, remove jars from canner and let cool. Sealed jars are shelf stable for up to one year.