Preheat oven to 350 degrees F. Heat oil in a large saute pan over medium-low heat. Add garlic and cook until soft and golden, about 1 minute. Add diced tomatoes with juice, tomato sauce, red peppers, chili peppers, cumin, coriander and 1/4 teaspoon each salt and pepper. Bring to a boil, then reduce heat to medium-low and simmer for 10 minutes until sauce thickens slightly. Remove from heat, and remove chile peppers.
Place Swiss chard on the bottom of a 9 by 13-inch glass baking dish. Season fish fillets with remaining salt and pepper and place in on top of chard. Cover with sauce and bake, covered, until fish is just cooked and chard is wilted, about 15 minutes. Remove cover and bake an additional 5 minutes. Sprinkle with cilantro and serve.