Preheat oven to 375°F. Place 12 cupcake liners in a muffin pan. (See Notes below for baking in a square pan or cast-iron skillet.)
Mix cornmeal, flour, baking soda, salt, and sugar in a large bowl, then whisk to mix. Add sour cream and butter. Stir. Add eggs and stir until combined.
Divide the batter between the muffin cups. Bake 20 minutes or until a toothpick comes out clean or with crumbs.
Notes
Making Muffins with Pan Liners
If making without the cupcake liners, grease the muffin tins.
Making a Loaf Instead of Muffins
If making this recipe in a single pan instead of a muffin pan, use either an 8-inch round cast-iron pan or an 8 x 8-inch square pan.
For the cast-iron pan, heat 1 tablespoon of butter in the pan as the oven heats. Then coat the pan by swirling the melted butter; then add the batter.
If using a square pan, spray it with cooking spray before adding the batter.
Cooking time for either pan is 25 minutes, or until the bread is golden brown on top, and a toothpick comes out clean or with crumbs.