In a medium bowl, place the red onion and lime juice in the bottom while you gather the remaining ingredients (a few minutes in a little acid will soften the red onion’s onionyness). Add in the cumin, coriander, chili powder and cilantro and stir to combine. Toss in the beans, olive oil and salt and toss to combine with the other ingredients. Taste for seasoning adding more salt, oil or lime juice if necessary. Serve immediately or refrigerate until ready to serve.
Tip: This only gets better with age, so feel free to whip this up a day or two in advance!