Reduce the Cider: In a small saucepan over medium-low heat, gently simmer 1.5 cups of pure apple cider for 15 to 20 minutes until reduced to exactly 1/2 cup of concentrated cider. Set aside to cool to room temperature.

Preheat & Prep Pan: Preheat your oven to 350°F (175°C). Generously grease two 6-cavity standard donut pans with nonstick baking spray or melted butter.

Whisk Dry Ingredients: In a large bowl, whisk together the flour, baking powder, baking soda, ground cinnamon, nutmeg, allspice, and sea salt until thoroughly blended.

Whisk Wet Ingredients: In a separate medium bowl, whisk together the melted butter, room temperature egg, granulated sugar, brown sugar, buttermilk, vanilla extract, and cooled reduced apple cider until smooth and glossy.

Combine Batter: Pour the wet ingredients into the dry ingredients. Gently fold with a rubber spatula just until combined and no dry flour streaks remain. Do not overmix.

Pipe & Bake: Transfer the thick batter into a large gallon zip-top bag or piping bag and snip off the corner. Pipe the batter evenly into the greased donut pan cavities, filling each about 3/4 full. Bake for 11 to 13 minutes, or until the donuts spring back when gently pressed and a toothpick inserted comes out clean.

Butter & Cinnamon Sugar Toss: Allow donuts to cool in the pan for 5 minutes, then invert onto a wire rack. In a shallow bowl, whisk granulated sugar and ground cinnamon. Place melted butter in another shallow bowl. Dip both sides of each warm donut into the melted butter, then toss generously into the cinnamon sugar mixture to coat completely. Serve warm!