Cook the apple cider in a pot over medium heat until reduced to half, about ¾ cup, then set aside.
Preheat the oven to 350°F (180°C). Lightly grease and line a 9×5 loaf pan with parchment paper.
In a bowl, whisk together the flour, cinnamon, salt, baking powder, baking soda, and nutmeg.
Grate 1-2 red apples into a bowl. Squeeze out the juice, then measure 1 cup of grated apples.
In a large mixing bowl, whisk together the oil, brown sugar, eggs, grated apples, and reduced apple cider. Whisk in the dry ingredients until just combined.
Pour the batter into the prepared loaf pan.
Combine granulated sugar and cinnamon, sprinkle two tablespoons over the top, and bake for 50-60 minutes.
Let the pan cool on a wire rack for 15 minutes, then remove from the pan and cool completely. Brush melted butter over the sides and cover with the remaining cinnamon sugar. Cut into slices and enjoy!