Blueberry Jam (No Pectin)

0 Place a small plate in the freezer. 
1 Combine blueberries, lemon zest, lemon juice and sugar in a large pot. Heat on medium to high heat.
2 Stir blueberries frequently.
3 Once blueberries come to a boil and cook for an additional 10-15 minutes on medium heat. The blueberries should start to slightly thicken.
4 Remove plate from freezer and add a small spoonful of blueberry jam. Place plate back into the freezer for 1-2 minutes. Remove plate from freezer run a finger through the jam if it stays separated and doesn't run your jam is done.
5 Remove jam from heat. Spoon jam into mason jars leaving about 1 inch of space at the top of the mason jar. Let jam come to room temperature then refrigerate or freeze jam.