Bring a large pot of water to a boil. Carefully add the corn cobs and cook for 1½ to 2 minutes until tender. Remove from the pot and cool under cold running water.

Chop the other ingredients: halve or quarter the cherry tomatoes, finely chop the red onion, and roughly chop the cilantro.

In a large mixing bowl, combine the corn, tomatoes, onion, and cilantro. Squeeze lime juice over the mixture, season with salt and black pepper, and stir gently.

Cover and chill in the refrigerator for at least 1 hour.

Just before serving, dice the avocado and fold it in gently. Serve with extra lime wedges and chili powder.