In a medium saucepan over medium heat, melt the butter and sugar together until bubbling.
Mix in berries and lemon juice, stirring to combine.
Increase the heat to high and bring the mixture to a rolling boil. Stir often for 10 minutes.
Use a spoon to mash down any large pieces of berries until the desired consistency is reached.
Once the jam has reached a jam-like consistency and sweetness, turn off the heat.
Carefully ladle hot jam into sterilized jars or containers.