Preheat the oven to 350°F and grease the donut pans if not using silicone donut pans.
Mix together the milk and vinegar in a small bowl and let sit for at least 5 minutes.
Stir together all of the dry ingredients for the donuts.
Add in the pumpkin puree, vegetable oil, and vanilla extract, and stir well.
Pour, or spoon in, about ¼ cup of the batter into each donut cavity. The batter should fill the donut cavities about ⅔ of the way up; if it doesn’t, adjust it until it does.
Bake the donuts for about 13 minutes, using a toothpick to check when they are done. Allow the donuts to cool for at least 10 minutes before topping.
Make the icing by stirring together the milk, vanilla, and powdered sugar.
Once the donuts are cool, ice them by dipping them in the icing or spooning the icing onto the donuts and spreading it. Then add a few pinches of pecans on the donuts as desired, then enjoy!