Preheat the oven to 350 degrees Fahrenheit.

Lightly spray a 9x13 baking dish with baking spray.

Remove cherries from jar, reserving liquid for frosting. Slice cherries in halves, then in quarters. Keep some cherries with stems for garnish.

In a large bowl, combine the dry cake mix and cherry Dr Pepper. Mix on low until just combined.

Stir in sliced cherries with a large spoon.

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

In a mixer, cream softened butter and 1/4 cup of reserved cherry juice until smooth.

Gradually add powdered sugar until a firm frosting forms. If too thin, add more powdered sugar.

Spread frosting over cooled cake.

Gently score the cake into servings, garnish each with a cherry stem if available.

Chill in refrigerator for 30 minutes to set frosting.

Sprinkle chocolate shavings over the frosting before serving.