Tip: You'll want to cook this in a wide pan. This helps to speed up the gelling process so no pectin is needed. Here's another tip: Be sure to crush the strawberries with a potato masher while cooking. This will also help thicken it up.
Before you get started, put a small plate in the freezer. (More on that in a few.)
In a 10 or 12 inch wide skillet, combine the sugar, lemon zest, and lemon juice and cook over very low heat for for about 10 minutes, until the sugar is well dissolved. Add the strawberries and continue to cook over very low heat for 20 to 30 minutes, until the strawberries release some of their juices and the mixture is boiling slowly. Give the berries a mashing, and continue to cook until a small amount of the juice will gel on a very cold plate. This is where that plate from the freezer comes into play.
Once your jam is sufficiently thick, pour carefully into 2 pint canning jars, seal and keep refrigerated or serve immediately. If not using within a couple of days, be sure to sterilize your jars and use proper canning guidelines.
Recipe by About a Mom at https://www.aboutamom.com/martha-white-muffins-fresh-strawberry-jam-cma-awards/