1. In a small saucepan set over high heat, bring the apple cider to a boil. Cook until juice is reduced by half (about 10 minutes). Set the remaining 3/4 cup aside to cool.
2. Preheat oven to 350 degrees F. Grease and flour two 6-portion donut pans, or one 12-cup muffin pan.
3. In a medium bowl, whisk together the flour, baking powder, spices, and salt. Set aside.
4. In the bowl of a stand mixer (or in a medium bowl using a hand mixer), combine softened butter with brown and white sugars; beat on high until very light and fluffy, about 3 minutes.
5. Scrape down the bowl and beat in the eggs, one at a time. Reduce speed to low and add the pumpkin puree and vanilla, beating until thoroughly combined.
6. With the mixer on low, alternate adding the flour mixture and the cooled concentrated apple cider. Once combined, beat the batter for an additional 30 seconds.
7. Pour the batter into a resealable plastic bag or piping bag with a 1/2-inch cut at the bottom. Pipe the batter into the donut molds or muffin cups (alternatively, you can spoon in the batter, but I find that a very messy process when using donut molds). Fill the molds/muffin cups about 2/3rds of the way.
8. Bake the donuts for 20-25 minutes, until they are golden brown, spring back to the touch, and a cake tester emerges clean (note that muffins may take a bit longer).
9. Allow to cool in the pan for at least 10 minutes, then transfer to a baking rack.
10. While the donuts are cooling, mix the cinnamon/sugar topping and melt the butter.
11. Brush the top, bottom, and sides of donuts with melted butter, then dip them in the cinnamon/sugar mixture, ensuring they’re coated evenly. If making muffins, brush the tops with butter and dip in cinnamon sugar.

Donuts are best eaten within a day or two of baking. Store leftovers at room temperature in a parchment-lined, airtight container.