Preheat your oven to 375°F and lightly coat a 9x13-inch baking dish with cooking spray. I found the bars easy to remove, but for extra assurance, you can line the greased pan with parchment paper and give it another light spray.
In a large mixing bowl, whisk together the flour, granulated sugar, brown sugar, baking powder, salt, and cinnamon.
In a separate small bowl, whisk together the egg and vanilla extract until combined.
Add the egg mixture and cold butter cubes to the dry ingredients. Using a fork, pastry cutter, or your hands, mix until the texture resembles coarse crumbs. I like using my hands—it’s quick, easy, and creates a well-mixed crumb topping.
Press half of the crumb mixture evenly into the prepared baking dish.
In another bowl, toss the strawberries, granulated sugar, cornstarch, and lemon juice together until the berries are evenly coated.
Spread the berry mixture over the crust, then sprinkle the remaining crumb mixture on top.
Bake for about 45 minutes, or until the top is golden brown.
Let the bars cool for 20 to 30 minutes before cutting into squares. Store them in an airtight container in the fridge. If you like them warm, just pop a bar in the microwave for 10 to 15 seconds.
