• Preheat oven to 350°F (175°C). Butter an 8 x 8-inch baking dish; set aside.

Prepare Topping:

• Whisk together flour, brown sugar, cinnamon, and salt in a medium bowl.
• Stir melted butter into flour mixture, pressing it together until it clumps. Set aside while you make the filling.

Prepare Filling:

• Combine blueberries, granulated sugar, cornstarch, 1 tablespoon lemon juice (save the rest for something else), lemon zest, and salt in a large bowl. Mix well.

Assemble + Bake:

• Transfer blueberry mixture to prepared baking dish, spreading in an even layer. Scrape any juice / sugar remaining in the mixing bowl into the baking dish.
• Using your hands to crumble topping over berries.
• Bake until topping is browned and blueberry filling is bubbling, about 45 to 50 minutes.
• Let cool at least 30 minutes, then serve plain or topped with ice cream. Enjoy!