Preheat your oven to 375°F.
Line a 12-cup muffin pan with paper liners.
In a medium bowl, whisk flour, baking powder, baking soda, and salt.
In a large bowl, whisk melted butter and sugar until combined.
Add eggs, sour cream, milk, and vanilla.
Whisk until smooth and creamy.
Toss diced strawberries with 1 tablespoon flour in a small bowl.
Add the dry ingredients to the wet ingredients.
Stir gently with a spatula until almost combined.
Fold in the strawberries just until distributed.
Divide the batter evenly into the muffin cups.
Top with extra diced strawberries and coarse sugar.
Bake for 20 to 24 minutes.
Check for a golden top and a clean toothpick.
Cool in the pan for 10 minutes.
Move them to a wire rack.