8tablespoons(1 stick) unsalted buttermelted and cooled
1(11 oz) can whole corn kernels, drained (optional)
Adjust an oven rack to the middle position and heat the oven to 400 degrees. Grease a 12-cup muffin tin.
Whisk the flour, cornmeal, baking powder, baking soda, and salt together in a large bowl. In a medium bowl, whisk the sour cream, sugar, milk, melted butter, and eggs together until smooth. Gently fold the sour cream mixture into the flour mixture with a rubber spatula until just combined. Do not overmix. If using, fold in the corn kernels.
Using a greased ⅓-cup measure, portion the batter into each muffin cup. Bake until golden brown and a toothpick inserted into the center comes out with just a few crumbs attached, 15 to 20 minutes, rotating the pan halfway through baking.
Let the muffins cool in the pan for 5 minutes, then flip out onto a wire rack and let cool for 10 minutes before serving.