Preheat oven to 375 degrees F.

Prepare the Filling: In a large skillet over medium-high heat, warm the oil until hot. Add the onion, green pepper and cook, stirring occasionally, until softened, about 10 minutes. Transfer to a bowl and set aside.

Reduce the heat to medium and add the ground beef to the pan. Cook, stirring occasionally to break up the meat, until browned, for about 5 to 10 minutes. Once the meat is browned, add the onion mixture back to the pan. Stir in the corn, diced tomatoes, tomato paste, chili powder, cumin and salt. Stir well. Bring to a simmer, then reduce the heat to low and simmer for 20 minutes. Remove from the heat and let stand while preparing the cornbread topping.

Prepare the Cornbread Topping: In a bowl, whisk together the cornbread mix, milk and egg, until smooth.

Assemble and Bake the Pie: Stir the olives and shredded cheese into the beef mixture and pour it into a 9x13-inch baking dish, smoothing the top. Pour the cornbread batter over the filling, using a spatula to spread it into an even layer. Bake for 30 to 40 minutes, or until the top is golden brown and a knife inserted into the center comes out clean. Allow the pie to rest for 15 minutes before serving.