Preheat oven to 375°F (190°C) and line a standard 12-cup muffin tin with paper liners.

In a large mixing bowl, whisk together the flour, sugar, baking powder, and salt.

In a medium bowl, combine the milk, melted butter, egg, lemon zest, lemon juice, and vanilla extract until well blended.

Create a well in the center of the dry ingredients and pour in the wet mixture.

Fold gently using a spatula until just incorporated, ensuring no large pockets of flour remain.

Gently fold in the fresh raspberries to avoid crushing the fruit.

Distribute the batter evenly into the prepared muffin tin, filling each cup approximately 3/4 full.

Bake for 18 to 22 minutes, or until the tops are golden and a toothpick inserted into the center comes out clean.

Allow muffins to cool in the pan for 5 minutes before transferring to a wire rack to cool completely.