Preheat your oven to 375°F (190°C) and line a muffin tin with paper liners.
In a large bowl, whisk together flour, baking powder, salt, sugar, and cinnamon.
In another bowl, mix the melted butter, milk, eggs, and vanilla.
Pour the wet ingredients into the dry and mix until just combined.
Spoon the batter into the muffin cups, filling each about ¾ full.
Bake for 20 minutes or until a toothpick inserted into the center comes out clean.
Let them cool in the pan for 5 minutes, then transfer to a wire rack.
Notes
Don’t overmix the batter; it should be a bit lumpy.
• Use fresh cinnamon for the best flavor.
• Fill muffin cups ¾ full to avoid spill-over.
• Let the muffins cool before removing them from the pan.
• You can add a crumb topping for extra crunch.