Step 1: Prepare the Cake

Preheat oven to 400°F (200°C) and lightly grease a 9×13-inch pan.

In a large bowl, whisk together sugar and flour.

In a saucepan, melt butter over low heat. Add cocoa and Dr Pepper, stirring well.

Bring the mixture to a boil, then remove from heat immediately.

Pour the hot cocoa mixture over the flour and sugar, stirring until smooth.

Add eggs, buttermilk, vanilla, baking soda, cinnamon, and salt. Mix until fully combined.

Pour the batter into the prepared pan and bake uncovered for 25–30 minutes, or until a knife inserted in the center comes out clean.

Step 2: Make the Dr Pepper Spiced Pecans

In a skillet, pour ¼ cup Dr Pepper and bring to a boil.

Cook on high until reduced by half (about 3–5 minutes).

Lower heat and stir in butter until melted.

Add vanilla and stir in the pecans until well coated.

Sprinkle in sugar, cinnamon, salt, and clove. Stir continuously until the pecans are fragrant and evenly coated, about 3–5 minutes.

Remove from heat and let cool. (You can make these ahead and store them in an airtight container.)

Step 3: Prepare the Frosting

Reserve ½ cup whole spiced pecans for topping; chop the remaining pecans.

Start the frosting about 5 minutes before the cake finishes baking so it’s ready while the cake is still warm.

In a saucepan, combine butter, cocoa, and milk. Bring to a boil, stirring occasionally.

Remove from heat and whisk in powdered sugar, vanilla, cinnamon, salt, and chopped pecans until smooth and thick.

Pour frosting evenly over the warm cake and spread gently to the edges.

Top with the reserved whole spiced pecans for garnish.