Wash the strawberries thoroughly and remove the stems.
Cut the strawberries into appropriate sizes.
Put the strawberries and sugar in a pot.
Simmer slowly over medium-low heat, stirring constantly.
Skim off any foam and impurities.
Continue to stir and cook until the mixture thickens.
Add lemon juice and mix well.
Turn off the heat, let it cool, and pour into sterilized jars.