Step 1. Preheat the Oven:

• Preheat your oven to 180°C (350°F). Line a muffin tin with paper liners or grease it with butter.

Step 2. Make the Muffin Batter:

• In a large bowl, whisk together the flour, baking powder, baking soda, salt, and ground cinnamon.
• In another bowl, mix the granulated sugar, brown sugar, melted butter, eggs, vanilla extract, and milk until well combined.
• Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Be careful not to overmix.
• Fold in the diced apples gently.

Step 3. Prepare the Crumb Topping:

• In a small bowl, combine the flour, brown sugar, and cinnamon for the topping.
• Add the softened butter and mix with a fork or your fingers until the mixture resembles coarse crumbs.

Step 4. Fill the Muffin Cups:

• Divide the muffin batter evenly among the muffin cups, filling each about 3/4 full.
• Sprinkle the crumb topping generously over each muffin.

Step 5. Bake the Muffins:

• Bake in the preheated oven for 18-22 minutes or until a toothpick inserted into the center comes out clean.

Step 6. Cool and Serve:

• Allow the muffins to cool in the pan for a few minutes before transferring them to a wire rack to cool completely.