Preheat oven to 375. Cut squashes in half and scoop out seeds. Place squashes cut side up on a cooking tray and roast until soft and a little browned (about 25 minutes). Once cooked, scoop out squash and discard the skins.
Meanwhile, chop onion and garlic. Cook with olive oil over medium-high heat until soft. Add cumin, tomatoes, black beans, squash, salt and pepper and stir.
Add vegetable broth and bring to a boil. Reduce heat and simmer for 25 minutes.
Blend using a handheld blender or traditional blender.