Preheat oven to 425°F. Spray baking pan(s) with baking spray and set aside.
In a medium bowl, whisk together cornmeal, flour, baking powder and baking soda. Stir in rosemary.
In a large bowl, whisk eggs, sugar, buttermilk and oil until combined. Add flour mixture in two batches; fold until just combined.
Divide batter between 3 mini loaf pans, or 1 standard loaf pan. Bake until a toothpick inserted in center comes out clean, 20 to 25 minutes for mini loaves, 30 minutes for standard loaf. Let cool in pan for 5 minutes and then move to wire rack to cool completely.