Wash the strawberries and remove petals, then chop them into pieces.
Cover chopped strawberries with the sugar, cover it and leave it in the fridge over the night.
After 12 hours in the fridge, put it on the stove and start cooking on the low heat. Add the lemon juice.
While cooking, stir it slowly. Remove from the heat once it starts becoming thicker. Prepare glass jar, sterilise it, and heat it in the oven or microwave. The warm jam pour into the jar, put back in the oven for additional 15 min on 90°C and than close with the sterilised lid.
The hot jar wrap in the cloth and leave it cool off slowly flipping the jar upside down. Once it is cold, it is ready to use, or it can stay like this for several months. Always use the clean spoon for taking the jam.