Spray 12 regular-sized muffin cups with non-stick spray.
In a large bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, pumpkin pie spice, ginger, and clove.
Add butter, milk, and pumpkin puree, mixing until just combined.
Spoon batter into prepared muffin tin, filling each cup about 1/2 full. Using a teaspoon or small cookie scoop, scoop about 1 rounded teaspoon of Nutella into the center of each muffin cup. It's okay if the Nutella touches the edges of the muffin tin. It will likely run a bit from the center of the cup, but it will bake solidly.
Top the Nutella with the remaining batter. Each muffin cup will be about 3/4-full.Again, it's fine if Nutella is exposed and not completely covered.
Using a small knife or toothpick, lightly swirl the Nutella and the batter. It will be a little difficult because the muffin batter is so thick, but just be patient.
Bake at 350 degrees for 12-15 minutes, or until edges just start to turn golden brown, and a toothpick inserted near the center comes out clean.
Remove the pan to a wire rack to cool.
Allow the muffins to cool for 10-15 minutes. If you try to remove them from the pan before they've cooled enough, they can come apart a little from the swirls of Nutella still being melty. Cool them to 'warm'.
In a small bowl, whisk together sugar and cinnamon.
Dip tops of muffins into melted butter, then dip into cinnamon-sugar.