Preheat the oven to 180°C.
1. Start by mixing together the cumin, 1 teaspoon of the chilli powder, the garlic powder and salt. Drizzle the chicken breasts with 1 tablespoon of the olive oil. Then sprinkle with 1 teaspoon of the spice mixture. Set the rest of the spice mixture aside. Bake until the chicken is cooked all the way through, 15 to 20 minutes. Remove it from the oven. Cut the chicken into cubes and set aside.
2. Next, heat the remaining 1 tablespoon olive oil in a large pot over medium-high heat. Throw in the onions, green and red bell peppers and garlic. Throw in a tablespoon of the spice mixture used to season the chicken. Add a little extra chilli powder (about 1/4 teaspoon) for heat. Stir to cook the vegetables until they begin to turn golden brown, about 5 minutes. Add the cubed chicken and diced tomatoes, juice and all. Add the chicken broth, hot water and tomato paste. Stir to combine and bring the mixture to a boil. Reduce the heat to low. Add the drained black beans. Next, mix together the cornmeal with 1/2 cup water. Add the mixture to the pot, and then simmer the soup for 10 to 15 minutes. Give it a taste and add salt or seasonings as needed; be sure to not under salt it!
3. Cut the tortillas into uniform 2- to 3-inch strips. Stir most of them into the soup just before serving. This is what makes tortilla soup tortilla soup! Turn off the heat and get ready to serve it up. Ladle the soup into a bowl, then add avocado, red onion, sour cream, cilantro and extra tortilla strips to the top. The more toppings on tortilla soup, the merrier.