Step 1

Peel the clementines and cut each one in half through the middle to check for seeds.

Step 2

Put the fruit, in batches if necessary, in the bowl of a food processor and process until smooth.

Step 3

Pour the puree into a heavy pot and add the sugar and lemon juice. Bring the mixture to a boil, then turn down the heat a bit and boil for about 30-40 minutes, stirring fairly often. Do not cover the pot!

Step 4

The liquid will foam up at first, but will eventually get absorbed. The mixture will start to thicken and get a little deeper and glossier when it is ready. I like to freeze a small plate and test the jam by dropping some onto it and letting it cool. If the jam firms up, it's done. If not, keep boiling a little longer.

Step 5

When it is done, ladle it into clean jars and let cool on the counter. When it reaches room temperature, cover and refrigerate. It will keep at least 10 days in the fridge.