The strawberries should be ripe but firm. Wash them well, cut off their stems and place them in a bowl. Crush them using your hand.

Place them in a wide pot together with the sugar and the lemon juice.

Let them boil over strong heat stirring often with a wooden spoon until they reach 105°C (the jam should drop from the spoon like a thick jelly - check out the tips).

When it cools place it in sterile jars and store in the fridge.