Cook macaroni according to package directions. Drain; set aside. Combine salmon, yogurt, cucumber, carrot, mayonnaise or salad dressing, dillweed, º teaspoon salt, and 1/8 teaspoon pepper. Toss with pasta. Cover; chill 4 to 24 hours.
Meanwhile, for tomato cups, cut out Ω inch of the core from each tomato. Invert tomatoes. For each, cut from the top to, but not quite through, the stem end, making 6 wedges.
To serve, place tomatoes on plates. Spread wedges slightly apart; fill with salmon-pasta mixture.