Heat a Dutch oven coated with cooking spray over medium-high heat. Add onion, chile, red bell pepper, and garlic; sauté 5 minutes. Add broth; bring to a boil. Cover, reduce heat, and simmer 10 minutes. Remove from heat. Add the beans, juice, and cumin. Cover and let stand 5 minutes. Ladle about 1 1/2 cups soup into each of 5 bowls, and top each serving with about 3 tablespoons cheese and 1 1/2 teaspoons sour cream.
This soup derives its spiciness from the poblanos while sour cream helps mellow the heat and round out the flavors. The soup gets its name from the cooked peppers that are called rajas in Spanish.