Preheat the oven to 375°F (190°C) and line a muffin tin with paper liners.
In a large bowl, whisk together the flour, sugar, baking powder, and salt.
Gently fold in the raspberries so they are coated with the flour mixture.
In a separate bowl, whisk together the melted butter, eggs, milk, lemon zest, and lemon juice until well combined.
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 them about two-thirds full.
Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean.
Allow the muffins to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.