Preheat oven to 350ºF and line your muffin tins with 18 muffin/cupcake paper cups and set aside.
In a medium sized bowl, combine all the dry ingredients, including the sugars and stir with a wooden spoon until all the ingredients look evenly distributed.
In a stand up mixer with the paddle attachment, cream the butter until soft and then add all the dry ingredients at once and mix on low for about 2 minutes. Add the eggs, pumpkin and vanilla and mix on medium-high speed until light and fluffy, scraping down the sides of the bowl as necessary. Lastly, add your diced golden delicious apple and mix for 1 minute more.
Using an ice cream scoop, fill your muffin cups with your batter and bake at 350ºF for 25 minutes. The muffins should have nice fissures traversing the tops and the utmost edges should be slightly darker than the rest of the muffin. A wooden skewer inserted into one of the muffins will come out clean.