Preheat your oven to 375°F (190°C) and grease a muffin tin with non-stick spray or butter.
In a large mixing bowl, whisk together the flour, baking powder, salt, and 1/4 cup of sugar until well combined.
In a separate bowl, mix the milk, melted butter, egg, and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix.
Divide the batter evenly among the muffin cups, filling each about 2/3 full.
In a small bowl, combine the cinnamon and 1/4 cup of sugar for the topping.
Brush the tops of the batter with melted butter and sprinkle generously with the cinnamon sugar mixture.
Bake in the preheated oven for 15-18 minutes or until golden brown and a toothpick inserted into the center comes out clean.
Allow the cruffins to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.