Preheat your oven to 350°F (175°C).

Line a 12-cup muffin tin with paper liners or lightly grease each cup.

In a large bowl, combine the flour, granulated sugar, baking powder, salt, and ground cinnamon. Whisk until well combined.

In a separate bowl, whisk together the melted butter, eggs, milk, and vanilla extract until fully blended.

Pour the wet ingredients into the dry mixture and stir gently until just combined.

Evenly distribute the muffin batter among the prepared muffin tin, filling each about 2/3 full.

In a small bowl, combine flour, brown sugar, and cinnamon for the topping.

Add the softened butter and mix it in with your fingertips until the mixture resembles coarse crumbs.

Generously sprinkle the crumble mixture over the batter in each muffin cup.

Place the muffin tin in the preheated oven and bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.

Allow the muffins to cool in the tin for 5 minutes before transferring them to a wire rack.