Heat olive oil in a large saucepan over medium-high heat. Add onion, bell pepper, and garlic to pan; sauté 3 minutes. Stir in 3/4 cup water and next 9 ingredients (through diced tomatoes); bring to a boil. Reduce heat, and simmer 8 minutes. Stir in cornmeal; cook 2 minutes. Remove from heat; stir in cilantro. Serve with sour cream.