Clean strawberries and hulled (remove the floral part)
In a large bowl, crush strawberries with your hand.
Put a heavy-bottomed pan on heat, pour the crushed strawberries, add sugar and lemon juice.
Low the heat and stir until the sugar is dissolved. Increase the heat to high and bring the strawberries mixture to full boil. Add butter to reduce the foaming.
Stir and continue boiling, until the mixture temperature gets to 220 degrees F. If you don't have a thermometer, place a plate in a refrigerator (in advance) When it's like 10-12 minutes into boiling, pour a little bit of the strawberry into the plate and put back into the refrigerator for about 1 minute. If you can run your finger through(make a line) it is ready to be canned.
Skim off the foam (if there's any) off the top. Get your sterilized jar and fill it with jam. Leave space at the top, run a spoon or knife down the side of the jar(inside jam) to get rid of bubbles. Clean the jar rim with a wet clean paper towel, to remove any stickiness from the rim.
If you are making in a large quantity (or not ready to use) Place the jar back into a pot and boil with water. For about 10 minutes, turn off the heat, let the jar stays in the pot for 5minutes, then remove (remember it's hot) be careful while taking it out, you a jar lifter leave on your counter for about 24 hours without touching it. Refrigerate and you're done.
Refrigerate the jam.
Enjoy your jam.