Rinse beans and discard any debris. Add to a large pot along with the hot water from the tap. Cut the onion in half and add one half to the pot, setting aside the other half for later. Add the bay leaf and salt.
Bring to a boil, then reduce heat to a low simmer and cover. Simmer for about 2 hours, checking periodically to make sure the water has not completely evaporated. Add more hot water as needed.
After 2 hours, remove the onion half and bay leaf and discard. Chop the remaining onion half and add to the pot along with the diced jalapeño and cumin. Continue to cook for about 1 hour, until beans are tender.