Adjust oven rack to middle position and heat oven to 400 degrees F. Lightly butter or spray the 12 molds in a regular-size muffin pan or fit the molds with paper muffin cups. Alternatively, use a silicone muffin pan, which needs neither greasing nor paper cups. Place the silicone muffin pan on a baking sheet.

In a large bowl, whisk together the cornmeal, flour, sugar, salt. and baking powder. In a large glass measuring cup or another bowl, whisk the eggs, milk, and melted butter together until well blended. Pour the liquid ingredients over the dry ingredients and, with the whisk or a rubber spatula, gently but quickly stir to blend until batter is just combined and evenly moistened. Do not over-mix. Divide the batter evenly among the prepared muffin cups.

Bake muffins until light golden brown and toothpick or skewer inserted into center of muffins comes out clean, about 20 to 25 minutes, rotating muffin pan from front to back halfway through baking time. Transfer the pan to a wire rack to cool slightly, about 5 minutes. Invert muffins onto wire rack, stand muffins upright, cool 5 minutes longer, and serve warm.