Black Bean Soup with Chipotle Chiles

adapted from Epicurious.com

1 tablespoon olive oil
2 medium-size red onions, chopped
2 medium-size red bell pepper, chopped
4 garlic cloves, minced
4 teaspoons ground cumin
1 16-ounce package dried black beans (I used Rancho Gordo Vaquero Beans.)
1 tablespoon chopped canned chipotle chiles (I used two chiles.)
7 cups hot water
2 tablespoons fresh lime juice
2 teaspoons coarse kosher salt
1/4 teaspoon ground black pepper

1 cup plain nonfat yogurt
1/2 cup chopped seeded plum tomatoes
1/4 cup chopped fresh cilantro
1 cup salsa (I used Mrs. Renfro's Chipotle Corn Salsa.)

Heat olive oil in large nonstick skillet over medium-high heat. Add onions and both bell peppers and sauté until beginning to brown, about 8 minutes. Add garlic and cumin; stir 1 minute. 

Transfer mixture to 6-quart slow cooker. Add beans and chipotles, then 7 cups hot water. Cover and cook on high until beans are very tender, about 6 hours. 

Transfer 2 cups bean mixture to blender; puree until smooth. Return puree to remaining soup in slow cooker. Stir in lime juice, salt, and pepper.

Ladle soup into bowls. Spoon dollop of yogurt into each bowl. Sprinkle with tomatoes and cilantro and serve.