1. Heat oil in a large nonstick skillet over medium heat. Add onion and garlic; sauté 3 minutes or until tender. Add tomatoes and next 3 ingredients; cook 12 minutes. Stir in beans; cook 2 minutes or until thoroughly heated.
2. While tomato mixture cooks, bring 2 1/4 cups water and next 3 ingredients to a boil in a small saucepan. Add cornmeal, stirring with a whisk; cook 5 minutes over medium heat or until mixture is slightly thickened, stirring constantly. Remove from heat; stir in cheese and sour cream. Cover and let stand 5 minutes.
3. Stir cilantro into ragoût. Spoon polenta into individual bowls, and top with ragoût.