First, pour the Dr Pepper into a saucepan over medium heat and bring to a boil. Reduce to a simmer and cook until reduce by half. You will need 3/4 cup. (I just occasionally pour the Dr Pepper into a measuring cup and if it's not to 3/4 cup, put it back in the saucepan and keep cooking.) Once reduced, set aside (or in the refrigerator) to cool. (This can be done the day before and kept covered if you need to break the steps up into two days.)

Preheat oven to 350 degrees and line three 6-inch or 8-inch cake pans* () with cooking spray. Line with parchment paper and more cooking spray.

Whisk together flour, cocoa powder, baking soda, baking powder, and salt in a bowl. Set aside.

In a medium-sized bowl, combine sugar, oil, buttermilk, vanilla, and eggs. Mix with an electric mixer until combined. Add half of flour mixture and half of the Dr Pepper to the sugar mixture and mix until just combined. Repeat with second half of flour mixture and Dr Pepper; mix well.

Divide batter evenly among the cake pans and bake for 25 minutes, or until center is set and a toothpick inserted into the center of each cake layer comes out clean. Cool cake layers completely before frosting.

Add cherries to a blender and blend until smooth. Pour cherry puree into a small saucepan and bring to a simmer. Cook until mixture has thickened and texture resembles syrup. You will need 3 tablespoons. (If you don't care to reduce the cherries, you can always just use 3 tablespoons of cherry puree, cherry syrup, or cherry juice from jarred cherries, the flavor just won't be as strong. You might also need to add a little bit more powdered sugar.) Set aside to cool.

Cream butter on medium-high speed with an electric mixer. Add half of powdered sugar and mix on medium speed until combined. Add 3 tablespoons of cherry reduction, vanilla extract, and remaining powdered sugar. Mix on medium speed until all ingredients are incorporated. Spread frosting between cooled cake layers. Garnish cake with remaining cherries and football decorations.