Preheat the oven to 350°

For the Filling:

1. In a large bowl, toss the blueberries with the lemon juice and lemon zest.
2. In a small bowl, whisk together the flour and sugar. Sprinkle evenly on top of the blueberries and mix well. Set aside.

For the Topping:

1. In a small bowl, partially melt the butter in a microwave. You can do this on the stove too. Be sure to not melt it all the way.
2. In a medium bowl, mix the flour, sugars, salt and cinnamon until combined.
3. Add the partially melted butter and mix until large, dough crumbles form.

Putting it all together:

1. Pour the blueberry mixture into a 9x13 baking dish or casserole pan. Be sure to spread it evenly.
2. Crumble the dough mixture evenly on top of the blueberries.
3. Bake uncovered for about 40-50 minutes or until the crumble is golden brown and the blueberries are bubbling up the sides of the dish.
4. Allow the crisp to cool most of the way before serving.
5. Best served warm with a side of Chantilly cream, whipped cream or vanilla ice cream.