COOK onion, garlic, cumin and pepper flakes in oil in 4-quart saucepot on medium heat 3 minutes or until onion is tender; remove from heat.
PLACE 2 cans beans with liquid in batches with broth in blender; cover. Blend until pureed. Stir into saucepot. Stir in remaining beans, salsa and lime juice.
HEAT mixture to boil. Reduce heat to low. Simmer 30 minutes. Ladle 1 cup soup into each bowl; top with dollop of yogurt. Serve with crackers.