Rinse the berries then cut strawberries into halves or quarters. Place them in a large pot then add lemon juice and sugar. Mix everything well and let them rest for 5 minutes.
Bring the berries to boil on high heat then reduce heat to medium and let the berries simmer while stirring from time to time. If you like, use a potato masher to mash the berries as they simmer. The jam is ready when it has a gel-like consistency. Let it cool then place in a jar to preserve.
Notes
Use more sugar if you like. I often use less sugar in my recipes.