Makes 6 to 8 servings
Make Ahead: The soup is best served the same day it is made, but it can be made 2 days ahead.

In the hot Mediterranean region, cooks often serve cool soups as a refreshing appetizer (or even as the entire meal, depending on how deadening the heat is on that particular day). This chunky soup is from that tradition. It shouldn't be ice cold--if made ahead and chilled, remove it from the refrigerator for about an hour before serving. Be sure that the chicken broth is thoroughly degreased, as chilled chicken fat will feel gritty on the tongue.

2 tablespoons extra-virgin olive oil
2 pounds summer squash (zucchini and yellow squash in any combination),
scrubbed, cut lengthwise in half, then crosswise into 1/2-inch thick pieces
1/2 cup chopped shallots
2 medium baking potatoes, peeled and cut into 3/4-inch cubes
5 1/2 cups canned reduced-sodium chicken broth
1 1/2 teaspoons chopped fresh thyme or 1 teaspoon dried thyme
1 large ripe tomato, seeded and cut into 1/2-inch cubes
Salt and freshly ground black pepper to taste
Lemon wedges

1. Heat the oil in a large pot over medium heat. Add the squash and cook, stirring occasionally, until the squash is lightly browned, about 15 minutes. Add the shallots and cook until softened, about 3 minutes.
2. Add the broth, potatoes, and thyme and bring to a boil. Reduce the heat to low and partially cover the pot with the lid. Simmer until the potato is tender, about 25 minutes. Add the tomato and cook just until heated through (it should retain its shape), about 3 minutes. Cool to room temperature. (The soup can be made 2 days ahead, cooled, covered, and refrigerated. Let stand at room temperature for 1 hour before serving.)
3. Just before serving, season with the salt and pepper. Ladle into soup bowls and serve.