Use a can opener to carefully open the canned black beans, then pour them into a colander.
Thoroughly rinse the beans under cold water, then gently shake the colander to remove excess moisture.
Finely chop half of a red onion and a handful of fresh cilantro, then add them to a large mixing bowl.
Add the rinsed beans to the bowl with the chopped vegetables, distributing them evenly.
Squeeze the juice of a fresh lime over the mixture, releasing a bright, citrus aroma and vibrant color.
Drizzle a tablespoon of olive oil over the salad, coating everything evenly with a rich, fruity aroma.
Add a pinch of salt, pepper, and optional cumin to season, then gently toss the salad to combine all ingredients thoroughly.
Taste the salad and adjust the seasoning with more lime, salt, or pepper as desired.
Let the salad sit for 15–20 minutes at room temperature or in the fridge to allow flavors to meld and develop.
Garnish with additional cilantro if desired, then serve chilled or at room temperature for a bright, satisfying dish.