Preheat the oven to 425°F (220°C) and lightly grease a jumbo muffin tin with cooking spray.

In a medium bowl, combine the flour, sugar, baking powder, baking soda, cinnamon, and salt.

In another bowl, whisk together the egg, milk, and vegetable oil.

Add the dry ingredients to the wet ingredients and stir just until combined. Do not overmix. The batter should be slightly lumpy.

Prepare the streusel by mixing flour, cinnamon, brown sugar, and chopped walnuts in a bowl. Cut in the softened butter using a fork or pastry cutter until the mixture becomes crumbly.

Spoon about a heaping tablespoon of muffin batter into the bottom of each muffin cup.

Add a tablespoon of apple butter on top of the batter.

Sprinkle a portion of streusel over the apple butter layer.

Divide the remaining batter evenly between the muffin cups and sprinkle the remaining streusel on top.

Bake for 5 minutes at 425°F, then reduce the oven temperature to 375°F (190°C) and bake for 13–15 minutes, or until a toothpick inserted into the center comes out clean.

Allow muffins to cool slightly.

Whisk together powdered sugar and apple cider until smooth, then drizzle over the warm Apple Butter Muffins.