In a small bowl, combine 3/4 tsp kosher salt, 1/2 tsp cumin, 1/2 tsp smoked paprika, 1/2 tsp chili powder, and 1/4 tsp freshly ground black pepper to make the spice rub.
Pat the 4 boneless, skinless chicken breasts (pounded to even thickness) dry and season both sides evenly with the spice rub.
Heat 2 tbsp olive oil in a large skillet over medium-high heat.
Add the seasoned chicken to the hot skillet and cook about 5 minutes per side, or until no longer pink in the center. Transfer the chicken to a cutting board, let rest briefly, then chop into bite-sized pieces and set aside.
Reduce heat to medium. In the same skillet, add 1 small chopped yellow onion, 1 chopped red bell pepper, and 1 minced clove garlic. Add 1 tsp kosher salt, 1/2 tsp cumin, and 1/2 tsp chili powder. Cook, stirring frequently, until the onions are softened, about 4 minutes.
Add 1 1/2 cups jasmine (or other long-grain) rice to the skillet and stir for 1 minute to coat the rice with the oil and spices.
Pour in the drained can of diced tomatoes (14 oz) and 3 1/2 cups chicken broth. Increase heat to bring the mixture to a boil.
Once boiling, cover the skillet, reduce heat to low, and simmer for 15 minutes, or until the rice is tender and the liquid is absorbed.
Stir in 1 cup canned black beans (rinsed and drained), 1 cup corn (fresh or frozen), and the chopped chicken.
Sprinkle 3/4 cup shredded Monterey Jack cheese evenly over the top, cover, and let the cheese melt for about 2 minutes.
Serve portions topped with sour cream (use the 3/4 cup as desired), chopped avocado (1 large, chopped), cilantro, and lime wedges.