Prep the beans: Rinse the dried black beans under cool water and pick out any small stones or broken bits. No soaking needed for the slow cooker, though you can soak 6–8 hours to slightly reduce cooking time.
Layer the aromatics: Add onion, garlic, jalapeño, bay leaf, cumin, oregano, and smoked paprika to the slow cooker.
Stir in the tomato paste if using.
Add beans and liquid: Pour in the rinsed beans and 6 cups of water or broth. Stir to combine and make sure the beans are submerged by at least 1 inch of liquid.
Cook low and slow: Cover and cook on Low for 7–9 hours or on High for 4–5 hours, until the beans are tender and creamy inside. Stir once or twice if you’re around.
Season: When the beans are fully tender, stir in salt and pepper.
Start with 1 teaspoon salt, then taste and adjust. Add lime juice for brightness.
Adjust consistency: If the beans are too brothy, remove the lid and let them simmer on High for 15–20 minutes. For creamier beans, mash a ladleful against the side of the pot and stir back in.
Serve: Spoon into bowls or use for tacos, burritos, rice bowls, enchiladas, soups, or as a simple side.
Garnish with cilantro if you like.