Rinse the black beans under cold water to remove any debris, then add them directly to the crockpot. No soaking required, which makes this a quick prep.
Pour in the vegetable broth over the beans, ensuring they are fully submerged. This will be the cooking liquid that softens the beans and forms the base of the soup.
Chop the onion finely and mince the garlic cloves. Add both to the crockpot, spreading evenly over the beans.
Sprinkle the cumin and smoked paprika over the ingredients in the crockpot. Give everything a gentle stir to coat the beans and aromatics with the spices.
Set the crockpot to low and cook for about 8 hours. During this time, the beans will soften, and the aroma of smoky spices will fill your home.
Once the beans are tender and fragrant, use an immersion blender to blend the soup until creamy, or transfer part of the soup to a blender, blend until smooth, then return to the crockpot. Leave some beans whole for texture if desired.
Taste the soup and adjust the seasoning with salt or a splash of lime juice for brightness. Stir in chopped cilantro for fresh, green contrast.
Let the soup sit uncovered for 10 minutes to settle and meld the flavors, then ladle into bowls and serve hot, garnished with extra cilantro if you like.