Preheat your oven to 400°F (200°C).
Line muffin tin with paper liners.
Mix flour, sugar, baking powder, and salt.
Combine melted butter, egg, milk, and vanilla.
Pour wet ingredients into dry ingredients.
Stir until just combined, don't overmix.
Gently fold in the halved cherries.
Make streusel by mixing flour and brown sugar.
Cut in cold butter until mixture resembles crumbs.
Add cinnamon to streusel mixture.
Fill muffin cups ¾ full with batter.
Sprinkle streusel topping over each muffin.
Bake for 18-22 minutes until golden.
Cool in pan for 5 minutes.
Transfer to wire rack to cool completely.