Preheat oven to 425 degrees. Line a muffin pan with 12 muffin liners. If not using liners, grease the cups with nonstick spray. Set aside.
In a large bowl, add flour, baking powder, baking soda, salt, sugars, spices, and chopped pecans. Whisk together to combine well. In a medium bowl, add eggs, oil, and pumpkin. Whisk until smooth.
Add wet ingredients to the dry ingredients. Using a rubber spatula, gently fold the wet ingredients into the dry ingredients until just combined. This should take between 12-15 folds. It's okay if a little flour is still exposed. You don't want to overmix or else the muffins will be tough.
Scoop the batter into the prepared muffin pan. Fill the individual cups almost to the top. This will ensure a full, tall muffin. Make the topping by melting the butter in the microwave for 20-30 seconds. Add all the other ingredients and stir together until combined. Scoop about 1 tablespoon of the topping and spread it onto the top of each cup filled with muffin batter.
Place into preheated oven to bake at 425 degrees for 5 minutes. Then, reduce temperature to 350 degrees to bake for another 12-14 minutes or until a toothpick comes out clean when inserted in the center of a muffin.
Remove from oven and let the muffins cool in the muffin pan for 5 minutes. Then, gently remove the muffins from the pan and cool on a wire rack for another 15 minutes. Serve once cooled by themselves or with a little salted butter.