Rinse the dried black beans thoroughly under cold water, removing any debris or cracked beans. Place them into the crockpot directly.
Chop the yellow onion into small, even pieces. Mince the garlic cloves finely to release their aromatic oils.
Add the chopped onion and minced garlic to the crockpot with the rinsed beans. Sprinkle in the smoked paprika, cumin, and chili powder, then give everything a good stir to coat the beans evenly with the spices.
Pour the warm vegetable broth over the ingredients in the crockpot. Cover with the lid and set the slow cooker to low for about 8 hours, or high for 4-5 hours, until the beans are tender and the flavors meld together.
Once cooking is complete, check the beans—they should be soft and breaking apart easily. Use a potato masher or an immersion blender to blend part of the soup, creating a slightly creamy, textured consistency, leaving some beans whole for bite.
Stir in the freshly squeezed juice of one lime to brighten the flavors. Drizzle a tablespoon of olive oil into the soup for added richness and shine. Taste and adjust seasoning with salt if needed.
Let the soup sit uncovered for about 10 minutes to allow flavors to meld and the texture to thicken slightly. Serve in bowls, garnished with fresh herbs or a dollop of sour cream if desired, and enjoy the cozy, smoky aroma.