1. Preheat the oven to 400 degrees. In a large cast-iron skillet, warm 1 teaspoon of the olive oil over medium-high heat. Add the beef and brown, about 5 minutes. Using a slotted spoon, transfer beef to a plate. Wipe skillet with a paper towel.
2. Add the remaining olive oil and the onion, zucchini, carrot, celery, garlic, and red and green peppers to the skillet; saute until vegetables begin to soften, 5 minutes. Add the chili powder, cumin and cinnamon and saute 1 minute.
3. Stir beef, salsa and the corn (if using) and ketchup into vegetables; season with the salt.
4. Scatter the polenta over beef mixture and sprinkle the pepper Jack cheese over the top. Bake until polenta is heated and cheese is golden-brown, about 7 to 10 minutes.