Cook brown rice according to package instructions. Heat oven to 375°F. Bring a large pot of water to a boil. Cut peppers in half lengthwise, seed and devein peppers, boil 4 - 5 minutes, just until tender. Drain well and align in baking dish, set aside.
Heat 1 tablespoon oil in a large and deep skillet over medium-high heat. Add onions and sauté until golden about 5 minutes. Add garlic and sauté 30 seconds longer, transfer onion mixture to a plate. Add remaining 1 tablespoon oil to skillet, add chicken, sprinkle with 1/2 teaspoon chili powder, 1/2 teaspoon cumin, paprika and season with salt and pepper.
Cook, stirring occasionally, until cooked through, about 5 minutes. Reduce heat to medium-low, add tomatoes, onion mixture, black beans, corn, cooked brown rice, remaining 1/2 teaspoon chili powder, 1/2 teaspoon cumin, cilantro, lime juice and season with salt and pepper to taste. Cook just until heated through.
Add a heaping 1/2 cup of the mixture to each pepper half (and slightly press filling to fit). Pour enough water into bottom of baking dishes to reach 1/8-inch in height (careful not to pour it in peppers).
Cover baking dishes with foil and bake 30-35 minutes, until peppers are soft. Remove from oven, sprinkle tops evenly with cheese then return to oven to bake until cheese has melted, about 3 minutes longer.
Serve warm topped with more cilantro, sour cream and hot sauce if desired. Serves 5.
Approximate Nutrient Analysis per half pepper (not including sour cream and extra hot sauce):
210 calories, 7 g fat, 2 g saturated fat, 40 mg cholesterol, 300 mg sodium, 22 g carbohydrate, 4 g fiber, 5 g sugar, 16 g protein