Heat 2 teaspoons oil in large saucepan over medium-high heat until hot. Add 1 cup onions. Cook and stir 5 minutes or until tender. Stir in tomatoes, tomato paste, chili power, salsa, 1 teaspoon cumin, sugar and pepper. Reduce heat to medium-low. Simmer 30 minutes.
Heat remaining 1 teaspoon oil in large skillet over medium-high heat until hot. Add remaining 1 cup onions, 1 teaspoon cumin and garlic. Cook and stir 5 minutes or until onions are tender. Stir in beans. Cook 5 minutes or until heated through, stirring occasionally. Remove skillet from heat. Stir in yogurt.
Preheat oven to 375°F Spoon bean mixture evenly down centeres of torillas. Roll up tortillas; place in medium backing dish. Top with sauce.
Bake 20 minutes. Serve with dollops of nonfat sour cream and cilantro, if desired. Garnish with cilantro and red pepper strips, if desired.