Preheat your oven to 375°F (190°C).
Spray the muffin tin with non-stick baking spray or line it with parchment liners.
In a large bowl, combine the melted butter, sugar, and lemon zest. Whisk until well blended, then add the eggs and milk or buttermilk, mixing until smooth.
In a separate bowl, whisk together the flour, sugar, baking powder, and baking soda until there are no lumps.
Gradually add the dry ingredients to the wet mixture, stirring gently until just combined.
Gently fold in the blueberries until evenly distributed.
Spoon the batter into the prepared muffin tin, filling each cup about two-thirds full.
Bake for 20-25 minutes, or until a toothpick inserted comes out clean.
Let the muffins cool in the tin for about 5 minutes before transferring them to a wire rack.
