Combine the wet ingredients and the sugar. Mix until they are fully incorporated.
Sift dry ingredients together and add to the wet mixture and mix until incorporated.
Put the batter into a greased 8" square pan, or greased muffin tins.
Bake for approximately 45 minutes for the cake, or 25-30 minutes for the muffins, or until a toothpick inserted into the center comes out clean.
Notes
Substitutions
To make gluten free, replace the flour with and equal amount of gluten-free flour mix and add 1/4 tsp xanthan gum. Also, the first time I made these gluten-free, I only used 1 tsp of baking powder, and the centers fell a bit. I think the extra 1/2 tsp of baking powder should correct the problem.
You can substitute the following spices instead of a pre-mixed pumpkin pie spice: 1/2 tsp ground nutmeg + 1 tsp ground cinnamon + 1/2 tsp ground cloves + 1/2 tsp ground ginger.
Corn Substitutions: Corn is a common ingredient in products. Starch, modified food starch, dextrin and maltodextrin can be from corn. Consult with your physician to find out which corn derivatives you need to avoid. Many corn-free options are available in the US. Find out more about corn substitutions.
Gluten: Gluten is a protein found in specific grains (wheat, spelt, kamut, barley, rye). Other grains are naturally gluten-free but may have cross-contact with gluten-containing grains. Look for certified gluten-free products if you need to avoid gluten. Find out more about wheat and gluten substitutions.