How to Make It
In a large saucepan, cover the beans with cold water and bring to a boil. Cover and let stand off the heat for 1 hour.
Drain the beans. Return them to the pot and cover with 3 inches of water. Bring to a boil and simmer over low heat until tender, about 1 hour and 30 minutes; season generously with salt during the last 10 minutes. Drain and let cool.
Meanwhile, in a medium saucepan, combine the quinoa with 2 cups of water and a pinch of salt and bring to a boil. Cover the saucepan and simmer the quinoa over low heat until the water has been absorbed, about 15 minutes. Spread the quinoa on a plate and let cool.
In a large bowl, whisk the vinegar, soy sauce, lime juice and chipotle. Add the olive oil in a thin stream, whisking until blended. Add the black beans, quinoa, scallions, red onion, yellow pepper and cilantro. Season with salt, toss to combine and serve.