Rinse beans until runoff looks clear, drain thoroughly and blot gently on a clean towel for 5 minutes.
Thaw corn completely, drain and blot. Cool cooked fresh corn before using.
Cover diced red onion with cold water 10 minutes, then drain and blot.
Dice bell pepper, quarter tomatoes and chop jalapeño and cilantro.
Whisk lime zest and juice, oil, garlic, cumin, chili powder, maple syrup, salt and pepper until slightly thickened.
Toss corn, bell pepper, tomato, onion, jalapeño and cilantro in the dressing.
Add dry black beans last and fold gently six to eight times with a wide spatula.
Refrigerate 30 minutes, then taste and add lime by the teaspoon or salt by a small pinch.
Add avocado only to the portion being served.
