In a small saucepan, bring the apple cider to a gentle boil. Allow it to simmer over medium heat until it thickens and is reduced to about 1/3 cup, which should take approximately 15-25 minutes. Once done, remove the saucepan from the heat and set the reduced apple cider aside to cool.

Preheat your oven to 350°F (175°C). Lightly grease two 6-cavity donut pans with cooking spray to prevent the donuts from sticking during baking.

In a large bowl, whisk together the gluten-free all-purpose flour, baking powder, ground cinnamon, ground nutmeg, ground cardamom, and kosher salt. In a separate bowl, whisk together the eggs, granulated sugar, brown sugar, oil, milk, vanilla extract, and lemon juice until well combined.

Add the wet ingredients to the bowl with the dry ingredients, followed by the cooled, reduced apple cider from Step 1. Whisk everything together until the batter is smooth and evenly mixed. Pour the batter into a large Ziploc bag, snip a 1-inch hole in one corner, and pipe the batter evenly into the greased donut pans.

Bake the donuts in the preheated oven for 10-12 minutes, or until they spring back lightly when touched. Remove the pans from the oven and gently turn out the donuts onto a cooling rack. Allow them to cool for 5-10 minutes, or until they are cool enough to handle. I like to let them firm up a bit as it makes coating them easier.

In a medium bowl, mix together 1 cup granulated sugar, 2 teaspoons ground cinnamon, and 1/4 teaspoon ground nutmeg. Dip each warm donut on both sides in the melted butter, then generously coat the donuts in the cinnamon sugar mixture. For an extra burst of flavor, I like to double-dip them for a thicker coating.