2 cups apple cider – reduced to 0.5 cup and cooled
4 cups all-purpose flour
2 tsp baking powder
0.5 tsp baking soda
1 tsp kosher salt
1.5 tsp ground cinnamon
0.5 tsp ground nutmeg
6 tbsp unsalted butter – softened
0.75 cups granulated sugar
0.25 cups light brown sugar – packed
2 large large eggs – at room temperature
2 tsp vanilla extract
0.5 cups buttermilk – at room temperature
0.5 cups all-purpose flour – for dusting
8 cups vegetable oil – for frying
1 cups granulated sugar – for coating
1 tbsp ground cinnamon – for coating
Instructions
Simmer the apple cider in a small saucepan over medium heat until reduced to 0.5 cup, 15–20 minutes; it should be syrupy and measure 0.5 cup. Cool completely.
Whisk together 4 cups flour, baking powder, baking soda, salt, 1.5 tsp cinnamon, and nutmeg in a mixing bowl.
In a separate large bowl, cream the butter with 0.75 cup granulated sugar and the brown sugar until light and fluffy, 2–3 minutes.
Beat in the eggs one at a time, then mix in the vanilla until smooth.
Stir in the cooled reduced cider and the buttermilk until evenly combined.
Add the dry ingredients to the wet and mix just until a soft, cohesive dough forms and no dry flour remains.
Scrape the dough onto plastic wrap, pat into a 1-inch-thick disc, wrap tightly, and chill until firm enough to roll, about 1 hour.
For the coating, mix 1 cup granulated sugar with 1 tbsp ground cinnamon in a shallow bowl; set aside.
Pour vegetable oil into a heavy pot to a 2-inch depth and heat to 350°F over medium heat, maintaining 350°F throughout frying.
Lightly flour a work surface with the 0.5 cup flour for dusting. Roll the dough to 0.5-inch thickness. Cut doughnuts with a 3-inch cutter, then punch out 1-inch holes; re-roll scraps as needed.
Fry doughnuts in batches without crowding, 1–2 minutes per side, until deep golden brown and cooked through; fry holes for 1–2 minutes total. Adjust heat to keep oil near 350°F. Drain on a rack set over a sheet pan for 1 minute.
While still warm, toss doughnuts and holes in the cinnamon-sugar coating to evenly cover. Serve warm or at room temperature.