1-First Step: Preheat and Prep the Dish Crank your oven to 350°F. Grab a 9×13-inch baking dish. Give it a quick spray with non-stick spray. This stops sticking and makes cleanup a breeze. Why 350°F? It bakes evenly without burning the top. Takes 5 minutes tops. Pro tip: Use glass or metal dish; both work great.

2-Second Step: Layer the Blueberries and Sugar Dump 3 cups fresh or frozen blueberries into the dish. Sprinkle 1/2 cup granulated sugar right over them. Stir gently to coat every berry. Watch the sugar pull out juices fast. It forms a thick syrup as it bakes. Frozen? No need to thaw; they release liquid perfectly. Stirring takes 1 minute. Smell that fresh berry goodness already?

3-Third Step: Mix the Cake Topping In a medium bowl, pour the entire 15.25 oz box of yellow cake mix. Add 1/2 cup melted butter. Use a fork to mix until crumbly. No need for perfection; lumps are fine. They create that textured crumble. Melt butter in microwave (30 seconds bursts) or stovetop. Takes 2 minutes. Hands stay cleanish!

4-Fourth Step: Sprinkle and Even It Out Scatter the crumbly mix evenly over the blueberries. Cover every inch for uniform baking. Press lightly if you want denser top, or leave loose for fluffier. Full coverage means no dry spots. Quick 1-minute job. Dish is oven-ready now.

5-Final Step: Bake, Cool, and Serve Bake at 350°F for 40 minutes. Look for golden brown top and bubbly edges. Toothpick in center should come out cleanish with some fruit. Cool 10 minutes on rack. Serve warm with vanilla ice cream or whipped cream. Scoop generous portions. Ice cream melts into sweet pools. Total magic!