Pour 2½ cups apple cider into a small saucepan. Bring to a gentle boil over medium heat and cook until reduced to 2 cups, about 25–30 minutes. Carefully check the volume using a heat-safe liquid measuring cup; continue simmering if needed.
2 ½ cup apple cider
Stir the oats into the reduced cider. Bring to a simmer and cook for 5 minutes, stirring occasionally. Transfer the oat mixture to a large mixing bowl and let cool until lukewarm before adding the eggs.
1 cup Old Fashioned Oats
While the oats cool, preheat the oven to 350°F and grease a 9 × 5-inch loaf pan.
Add the eggs, melted butter, brown sugar, and granulated sugar to the cooled oat mixture. Stir until well combined, breaking up any large clumps of oatmeal.
2 large eggs, ½ cup unsalted butter, ⅓ cup dark brown sugar, ⅓ cup granulated sugar
In a separate bowl, whisk together the flour, cinnamon, cloves, salt, baking powder, and baking soda. Add to the oat mixture and stir gently just until combined and no dry flour remains. Do not overmix.
2 cups All-purpose flour, 2 teaspoons ground cinnamon, ¼ teaspoon ground cloves, 2 ¼ teaspoons baking powder, ½ teaspoon baking soda, ¼ teaspoon salt
Spoon the batter into the prepared loaf pan and spread evenly. Bake for 45–50 minutes, or until a toothpick inserted into the center comes out without wet batter. A few moist crumbs are fine.
Let the bread cool for about 20 minutes. Remove from the pan and place on a wire rack to cool completely before glazing.