Toast the pine nuts in a dry saucepan over medium heat until light brown and fragrant, 3 to 4 minutes, shaking pan now and then. Remove and set aside.
Add the broth to the pan and bring to a boil. Stir in the couscous, cover, and remove from the heat. Let stand for 5 minutes, or until the liquid is absorbed. Fluff with a fork.
Put the lemon juice in a large serving bowl. Gradually whisk in the oil in a slow steady stream until it is incorporated and slightly thickened. Whisk in the salt and pepper.
Stir in the remaining ingredients. Serve immediately or refrigerate for up to 4 days.
Tip: To quickly seed a tomato, cut it in half crosswise, then dig out the seeds and gel from each half with the tip of your knife.