Preheat the oven to 300℉. (That’s a little lower than usual－not a typo.) Grease a 6-cup donut or jumbo muffin pan and set aside. (You may use a regular muffin pan. You will simply need to add a few minutes to the bake time.)
In a medium mixing bowl, whisk the eggs, and then stir in the remaining wet ingredients. Add the dry ingredients, and stir until smooth. Transfer the batter to the donut or muffin pan, evenly filling the cups, and sprinkle with coarse or cinnamon sugar, if using.
Bake for 10-15 minutes and remove the pan as soon as the donuts are just firm in the center. (Check after 10 minutes, adding time, as needed, until you know how long these take in your oven. In my oven, the donuts take 13 minutes and the jumbo muffins take 15 minutes. Precise time will vary slightly based on oven and pan used.)
Cool for several minutes and then remove to a cooling rack. Eat, as is, or frost as desired once completely cool.
Storage: The donuts will stay fresh for 3-4 days when stored in an airtight container either in the refrigerator or at room temperature. If frosted with an ingredient that requires refrigeration, like cream cheese, opt for the fridge. Unfrosted, the baked and cooled donuts freeze well, too.