Rinse and cut the strawberries.

Add sugar and leave it to rest for one hour.

Prepare clean glass jars.

On a medium heat, in a pot, cook the mixture for 10 minutes.

Add citric acid or lemon juice and sugar mixed with pectin.

Cook for another 10 minutes.

If any foam appears, take it away with a spoon.

Pour the jam into the glass jars and close them.

Let the jars cool before stored to a cool, dry and dark place.