Toss 2 cups of beans (or if you bought canned, just add one can here), the salsa and broth into a blender or food processor. Pulse a few times to lightly mash the beans and reduce some of the chunkiness of the salsa (and if you feel your family would like their soup smoother, feel free to blend more).
Place bean mixture into a large sauce pan over medium heat; add the remaining beans, cumin and coriander. Heat through.
Serve with a small amount of Greek yogurt (which serves as a nutrient dense alternative to sour cream) and fresh parsley on top, baguette and watermelon on the side.