1. Place the avocado in the bottom of a nonreactive mixing bowl and gently toss it with 2 tablespoons of the lime juice. Spoon the tomato on top of the avocado.
2. Cut the kernels off the corn. The easiest way to do this is to lay the cob flat on a cutting board and remove the kernels using lengthwise strokes of a chef's knife. Add the corn kernels to the mixing bowl. The salsa can be prepared to this stage up to 2 hours ahead. Refrigerate it, covered.
3. Just before serving, add the jalapeño(s) and cilantro to the mixing bowl and gently toss to mix. Taste for seasoning, adding more lime juice as necessary and season with salt and pepper to taste; the salsa should be highly seasoned.
- Christiana Thomas