- 1 box yellow cake mix
- 2 eggs
- 1/2 Cup butter, melted plus 2 tablespoons cold butter, cut into chunks
- 1 Teaspoon lemon juice
- 2 Cups blueberries, fresh or frozen and thawed
- 1/2 Cup plus 1 tablespoon flour
- 1 Tablespoon cinnamon sugar
- 2 Tablespoons brown sugar
- 1/3 Cup quick cooking oats
Preheat the oven to 350 degrees.
Liberally grease an 8×8-inch baking pan with cooking spray and set aside.
In a large bowl, combine the cake mix, eggs, melted butter, and lemon juice until a thick yet soft dough forms. Spread the entire mixture evenly onto the bottom of the pan.
In a small bowl, toss together the blueberries, the tablespoon of flour, and 1 tablespoon of cinnamon sugar lightly. Spread the blueberry mixture evenly on top of the dough in the pan.
In another small bowl, lightly mix the remaining flour, brown sugar, and oats together. Using a fork or pastry blender, cut the 2 tablespoons of cold butter into the flour mixture until it resembles coarse crumbs. Sprinkle chunks of the crumbs on top of the blueberry layer evenly.
Bake until the top is golden and the center is just about set, about 15-18 minutes. Do not overbake.
Allow the bars to cool completely in the pan before cutting them into squares to serve. Leftovers can be stored in an airtight container at room temperature for about a day.