Preheat oven to 350 degrees. While waiting for that to heat up with a blender add De - stemmed cherries and grind them until cherries turn into small chunks. Pour brownie mix into a medium-sized bowl, add cherries and cherry juice now pour in your 12 oz. can of diet Dr. Pepper. With a whisk, combine ingredients until there are no lumps. Pour mixture into a 9 x 9-inch pan coated with cooking spray and bake according to the package directions, adding an additional 5 to 10 minutes to the baking time. Your brownies should bake for about 40 to 45 minutes, or until a toothpick inserted comes out clean. Allow to cool for about 5 minutes and OH MY GOSH BEST THING EVER!!