Preheat the oven to 400°F. Grease a 9x5 loaf pan and set aside.
In a mixing bowl, add the cornmeal, flour, baking soda, salt, cream of tartar, and sugar, then whisk until combined.
In a separate bowl, whisk together the egg, sour cream, milk, and melted butter.
Pour the wet ingredients into the dry ingredients and mix until just combined.
Transfer the batter to the prepared loaf pan and spread evenly.
Bake on the middle rack for 30-35 minutes, or until golden brown and set in the center.
Remove from the oven and serve warm.