½cupunsalted butter, cold and cut into thin slices
Optional: 1 teaspoon cinnamon
Optional: ½ cup chopped pecans or walnuts
Instructions
Step 1: Prepare Your Baking DishPreheat your oven to 350°F (175°C). Lightly grease a 9x13 inch baking dish with cooking spray or butter. This ensures easy serving and cleanup later—a step 43% of novice bakers reportedly miss.Step 2: Add the Blueberry LayerSpread your blueberries evenly across the bottom of the prepared baking dish. Sprinkle the sugar over the berries, then drizzle with lemon juice. If using cinnamon, dust it over the berries now. The acid in the lemon juice helps brighten the berry flavors while balancing the sweetness.Step 3: Add the Cake Mix LayerEvenly distribute the dry cake mix over the blueberry layer. Don't mix it in—simply sprinkle it to create a uniform layer across the top. Pat it down very gently if needed, but avoid pressing too hard.Step 4: Add the Butter LayerArrange the thin slices of cold butter evenly across the top of the cake mix. Aim for complete coverage as this will ensure the cake mix properly hydrates and bakes into a golden crust. If using nuts, sprinkle them over the butter now.Step 5: Bake to PerfectionPlace the baking dish in the preheated oven and bake for 45-50 minutes, or until the top is golden brown and the edges are bubbling. The cake is done when a toothpick inserted in the cake layer comes out clean, though it may have blueberry juice on it.