Preheat the oven to 450 degrees.Place the corn halves into a medium pot and cover with water and a pinch of salt. Bring to a boil and let cook for 2-3 minutes or until corn is cooked through (easily pierced with a fork.) Drain into a colander and set aside to cool.Once water boils, place a medium cast-iron skillet (or regular skillet will do) over medium heat and add in the olive oil. Once oil heats, add in the onions and bell peppers and cook for 5 minutes or until peppers and onions begin to soften. Then, add in the tomatoes, garlic, black beans and 1 tablespoon of the fajita seasoning. Toss and let cook for 2-3 minutes and then add in the cilantro and corn, shaving the corn off the cob into the skillet with a knife.Remove the skillet from the heat and sprinkle over with cheese. Place in the oven for 5 minutes or until cheese melts.Serve immediately, garnished with avocado slices.