Step 1In a mixing bowl, combine the beans, minced onion and cilantro. Add the lime juice, oil and cumin and mix well. Season with a scant one-half teaspoon salt and scant one-fourth teaspoon pepper, or to taste.
Step 2Stir in the red bell pepper, hearts of palm and grape tomatoes. Cover and chill 1 hour.
Step 3Just before serving, stir in the avocado. Taste and adjust the seasoning if necessary.