Blend the blueberries into 1 cup of puree.

In a pan mix blueberry puree and sugar.

Heat the mixture over medium high heat stirring until it boils.

Reduce heat to medium, stirring constantly while it simmers.

After 10 minutes of boiling, add the lemon juice.

Continue to stir every minute while it simmers until the jam consistency is obtained. This can take 15-25 minutes.

Pour jam into an airtight container but leave the container open until the jam cools completely.

Cover the container and put in the refrigerator