Preheat oven to 375°F (190°C) and line a 12-cup muffin tin with liners.
Mix dry ingredients: In a large bowl, whisk flour, sugars, baking powder, baking soda, cinnamon, and salt.
Whisk wet ingredients: In another bowl, whisk eggs, oil, milk, and vanilla.
Combine: Add wet to dry ingredients and stir gently. Fold in diced apples.
Make crumb topping: Stir flour, brown sugar, cinnamon, and melted butter until crumbly.
Assemble muffins: Fill muffin cups 3/4 full. Top each generously with crumb topping.
Bake: 18–22 minutes, until a toothpick comes out clean. Cool in pan 5 minutes, then transfer to rack.