1. Trim off any wilted or discolored edges from chard leaves. Cut the leaves away from the stalks. Trim bottoms of stalks. With a small knife, peel away the transparent membrane attached to the stalk on both sides. Wash leaves and stalks separately in cold water several times to get rid of grit; drain well. Cut leaves and stalks crosswise into 2" lengths.
2. Boil the stalks, uncovered in 4 quarts boiling water with 1 teaspoon salt until barely tender and tested with a fork, about 15 to 20 minutes.
3. Add leaves and cook for an additional minute. Transfer to a colander, refresh under cold water and drain well. Squeeze out any excess moisture with your hands.
4. In a 12" skillet, heat olive oil over medium-high heat until haze forms. Turn heat to low and add garlic. Saute, stirring constantly, until very lightly golden, about 1 minute.
5. Add chopped tomatoes; cook, stirring constantly, for an additional minute. Add chard leaves and stems. Cook, covered, stirring once or twice, until stalks are very tender when tested with a fork, about 10 minutes. Transfer to a bowl and serve immediately.'