Wash the strawberries well and remove the leaves.
Chop them into medium size pieces
Add them in a cooking pan and then add sugar and mix.
Cover the pan let it rest for 2 hours .
Mash the strawberry slightly with a spoon.
Put the pan on the gas stove and cook on low heat till the sugar melts.
Now add lemon juice,mix and give it a boil.
Now remove the pan from the heat and with a spoon try to remove the scum formed on top of the jam (it helps to get a clear and bright colour jam)
Now add the lemon zest and cook the jam on low heat and keep mashing the strawberries in between.
When jam starts to thicken then add butter in it and mix.
Remember that the jam will thicken further when it cool down completely so cook accordingly.
Now do the plate test- -put a spoon full of jam in a plate and check ,if the water separates from the pulp then you need to cook it further,and if it remains at the same place then its done.
Let the jam cool down completely.
Store in a sterilized glass bottle and keep refrigerated.