How to Make It
Preheat oven to 375°F. Coat a 12-cup muffin pan with cooking spray.
Whisk together flour, cornmeal, sugar, baking powder, and pepper in a large bowl. Whisk together buttermilk, butter, and eggs in a large bowl until smooth. Add flour mixture to buttermilk mixture; stir with a wooden spoon or rubber spatula until smooth. Fold in chives, two-thirds (about 2 1/2 ounces) of prosciutto, 1/4 cup tomatoes, and 2 ounces cheese.
Divide batter evenly among cups of prepared muffin pan. Sprinkle muffins with remaining prosciutto, remaining 1/4 cup tomatoes, and remaining 2 ounces cheese.
Bake at 375°F for 20 minutes or until cheese melts and a wooden pick inserted in center of muffin comes out with moist crumbs. Remove from oven; cool on a wire rack 10 minutes. Carefully run an offset spatula or butter knife around edges to loosen muffins.