Preheat oven to 350 degrees F. Line a 12-count cupcake pan with paper liners and set aside.
Make the Muffin Batter: Add applesauce, butter, brown sugar, egg and egg yolk, and maple syrup to a mixing bowl and stir until combined.
2 ⅓ cup unsweetened applesauce, ⅔ cup unsalted butter, ½ cup brown sugar, 1 egg, 1 ½ tablespoon maple syrup
In another bowl, whisk together flour, baking powder, cinnamon, ginger, nutmeg, and salt.
2 cups all-purpose flour, 2 teaspoons baking powder, ½ teaspoon baking soda, 1 ½ teaspoon ground cinnamon, ¾ teaspoon ground ginger, ¾ teaspoon ground nutmeg, ¾ teaspoon fine sea salt
Add flour mixture to applesauce mixture and stir until just combined, scraping down the sides of the bowl as you go. Do not over mix the batter.
Make the Crumb Topping: In another bowl, mix together brown sugar, flour, butter, cinnamon, and salt until a crumbly topping forms.
½ cup brown sugar, ½ cup all-purpose flour, 6 tablespoons unsalted butter, 1 teaspoon ground cinnamon, ½ teaspoon fine sea salt
Assemble and Bake: Divide the muffin batter evenly between the lined cupcake wells, then sprinkle the crumb topping mixture over top, and gently press it into the batter.
Bake the muffins for about 25 minutes or until a toothpick inserted in the center-most muffins comes out clean. Cool in pan until comfortable to handle (about 20 minutes), then transfer to a wire cooling rack or serve warm.