Preheat your oven to 375°F (190°C). Line a muffin tin with paper liners.
In a large bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon.
In another bowl, mix the melted butter, granulated sugar, and brown sugar until well combined. Add the eggs, milk, and vanilla extract, and mix well.
Pour the wet ingredients into the dry ingredients and mix until just combined. Fold in the chopped apples.
Divide the batter evenly among the muffin cups, filling each about ⅔ full.
To make the crumb topping, mix the flour, brown sugar, and cinnamon in a small bowl. Add the melted butter and mix until crumbs form. Sprinkle the crumb topping evenly over the muffin batter.
Bake for 20-25 minutes, or until a toothpick inserted into the center of a muffin comes out clean. Allow the muffins to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.