1.In a medium-size saucepan, bring broth to a boil over high heat. Stir in couscous. Remove from heat. Cover and let stand until all the liquid is absorbed, about 5 minutes. Then fluff couscous with a fork. Transfer to a large metal mixing bowl and cool, uncovered, in the refrigerator while continuing with recipe.
2.Meanwhile, core, seed and chop tomatoes into small 1/4-inch (0.5 cm) pieces. You should have about 3 cups (750 mL). If making right away, finely chop mint leaves. Whisk oil with lemon juice, vinegar and salt. When couscous is cooled to at least a lukewarm temperature, stir in tomatoes. Then, stir in lemon juice mixture until evenly mixed. Stir in mint just before serving. Salad is best served at room temperature.