Cut the tomatoes vertically into 8 to 12 wedges each, depending on their size. Slide your thumb and forefinger along the sides of the wedges to take out the seeds. (Seeding isn’t essential but it helps keep the salad from getting watery. Thoroughly toss the tomato wedges with 2 teaspoons of the coarse salt and drain in a colander set over a bowl for 30 minutes.
Plunge the ears of corn in a pot of boiling water for about 5 minutes and drain. Thawed frozen corn can be used as is.
Slice the onion as thin as you can-a vegetable slicer makes this easy-and rub the slices thoroughly with 2 teaspoons of the remaining coarse salt. Drain the slices for 30 minutes in a strainer or colander set over a bowl. If you’re using jicama, peel and slice it into slices about 1/8 inch thick. Cut the slices into strips about 1/4 inch wide. Peel and halve the avocados and slice each half, lengthwise, into 6 strips. Sprinkle with salt and pepper and half the lime juice.
To prepare the sauce, crush the garlic into a paste on a cutting board with the side of a chef’s knife. Combine the garlic, minced chiles, and cilantro with the olive oil or crème fraiche and remaining lime juice.
Arrange the vegetables in a large salad bowl with the strips of peppers on top. Just before serving, pour over the sauce and gently toss.
Makes 8 side-dish servings