Preheat your oven to 350 degrees.
Oil your donut pan to prevent sticking and set aside.
In a large bowl, add the flour, baking powder, baking soda, salt, cinnamon and nutmeg. Mix until everything is incorporated.
In the other bowl, mix in the sourdough starter, maple syrup, vanilla extract, eggs, sour cream, and oil until well combined. This should create a frothy mixture from mixing the sourdough starter with other wet ingredients.
Add the dry ingredients to the wet ingredients and mix well with the dough whisk.
Next, chop the pecans and fold them into the dough with the silicon spatula.
Finally, take a spoon and start adding the batter to the donut pan. You can also fill up a ziploc bag with the batter and cut a hole at the bottom to create a piping bag if that's easier. Fill each donut well about 2/3 full.
Bake at 350 degrees for 15 minutes.
Once the donuts are done baking, let them completely cool in the pan before removing them.
While the donuts are cooling, melt butter in a bowl and add cinnamon and sugar to another bowl. Dip the donuts in butter and then in the cinnamon sugar mixture.