Preheat the oven to 350°F.

Lightly spray a 9x13 baking dish with baking spray.

Remove cherries from jar, reserve liquid for frosting, and chop 15 cherries in halves and halves again. Keep remaining cherries for garnish.

In a large bowl, mix cake mix and Cherry Dr. Pepper until just combined without water, milk, eggs, or oil.

Stir in chopped cherries using a large spoon.

Pour batter into the prepared baking dish and bake for 28 minutes, or until a toothpick inserted comes out clean. Cool completely.

Cream softened butter with reserved cherry juice using a mixer on medium speed.

Gradually add powdered sugar until frosting reaches desired consistency, similar to canned frosting, adding up to 0.5 cup extra if needed.

Spread frosting evenly over cooled cake.

Gently score the cake into servings. Garnish each piece with a stemmed cherry, slicing if needed.

Chill the cake in the refrigerator for 30 minutes to 1 hour to set the frosting.

Optional: Sprinkle chocolate shavings over the frosting for decoration.