Preheat the oven to 400 degrees.
In a medium bowl, add the flour, cornmeal, salt, baking soda, and baking powder. Mix to combine and set that aside.
In a large bowl, add the sugar and eggs. Add the sourdough starter, milk, and butter. Mix well to combine.
Add the dry ingredients to the wet ingredients and mix until just combined. The batter will not be smooth, it’s ok if there are a few lumps left.
Line a muffin tin with muffin liners. Scoop equal amounts of batter into the muffin tins. Bake for 18-20 minutes or until a toothpick is inserted and it comes out clean.
Allow the muffins to cool slightly and serve.