First things first, let's get the oven ready. Preheat it according to the directions on your chocolate cake mix box – it's usually around 350°F (175°C). While it's heating up, go ahead and grease a 13x9 inch baking pan really well. You want that cake to flip out beautifully!
Next, pour that lovely melted butter right into the bottom of your greased pan. Just tilt the pan around a little to coat the bottom evenly.
Now, sprinkle the brown sugar evenly over the melted butter layer. This is where the magic starts!
Carefully spoon the cherry pie filling over the brown sugar layer. Try to distribute it as evenly as you can so every slice gets plenty of cherries.
In a big bowl, grab your electric mixer. Add the chocolate cake mix, the eggs, vegetable oil, water, and that splash of vanilla extract. Give it a gentle mix on low speed for about 30 seconds just to get everything incorporated. Then, crank it up to medium speed and beat for 2 minutes. You want the batter to be smooth and well combined.
Here's the slightly tricky part, but you can do it! Carefully, and I mean carefully, pour the cake batter over the cherry filling in the pan. Try to pour it gently over the cherries instead of in one big blob. Once it's in, use a spatula or the back of a spoon to gently spread the batter to cover the cherry layer completely. Try not to disturb the cherry layer too much underneath.
Pop the pan into your preheated oven. Bake according to the time listed on your cake mix box, which is usually between 30-35 minutes. You'll know it's done when a toothpick inserted into the center of the cake comes out clean (avoiding the cherry layer, of course!).
Once it's baked, take the cake out of the oven and place the pan on a wire rack. Let it cool in the pan for 10-15 minutes. This is crucial! Cooling it too long makes the topping stick, but flipping it too soon can cause it to fall apart. That 10-15 minute window is just right.
Okay, the moment of truth! Grab the serving plate you want to use (make sure it's large enough!). Place it upside down over the cake pan. Using oven mitts, firmly hold the plate and the pan together, and in one swift, confident motion, flip the whole thing over! Set the pan down on the counter and let it sit there for a minute or two. Gravity will help the cake release.
Gently lift the pan off the cake. Ta-da! If any cherries or topping stick to the pan (it happens!), just carefully scrape them out with a spoon and put them back onto the cake.
Serve it up! This cake is absolutely divine served warm, maybe with a scoop of vanilla ice cream or a dollop of whipped cream. It's also lovely at room temperature. Enjoy every single bite!