Step 1: Preheat your oven to 350°F (175°C) and grease your loaf pan with cooking spray or line it with parchment paper for easy removal.
Step 2: In a large mixing bowl, combine the granulated sugar, brown sugar, and vegetable oil. Whisk until smooth. Add pumpkin puree, eggs, and buttermilk; mix until incorporated.
Step 3: In a separate bowl, whisk together flour, pumpkin pie spice, baking soda, and salt.
Step 4: Gradually add the dry ingredients to the wet ingredients, mixing gently until just combined.
Step 5: Gently fold in the chopped Reese’s Peanut Butter Cups, distributing them evenly throughout the batter.
Step 6: Pour the batter into the prepared loaf pan and smooth the top. Bake for 55-65 minutes, or until a toothpick comes out clean.
Step 7: Let the bread cool in the pan for 10 minutes, then transfer to a cooling rack to cool completely before slicing.