Place beans (and their soaking water) in large heavy pot

Bring to boil and skim off foam

Add onion, half the garlic and reduce to low

Add salt and cover for 1 hour

Add remaining garlic and more salt if desired

Simmer for another 30 minutes

Add cilantro and simmer for another 30 minutes, until beans are tender

While beans are simmering, wash amaranth leaves in water

Bring large pot of water to boil, fill another bowl with ice water

Add amaranth to boiling water, blanch for two minutes, add salt and transfer to ice water

Drain amaranth and chop coarsely

Stir amaranth into beans, let simmer for 5 minutes and serve