Heat oil in a 12 inch oven proof skillet over medium heat. Add onion, and seasonings and cook until onion is softened, about 5 minutes.
Add ground beef, olives, corn and tomatoes and bring to a simmer, cook until meat is cooked through, about 5 minutes. Stir in the cheese and season with salt and pepper to taste. If not using an oven proof skillet, pour into a baking dish.
Whisk the dry ingredients together in a large bowl. In a separate bowl, whisk together the egg and buttermilk and stir into the flour mixture until mixture is uniform. Stir in the melted butter until just combined.
Spoon cornbread mixture on top of beef mixture, spreading evenly. Bake until the cornbread is cooked through in the center, about 10-15 minutes.