2 tablespoons nonfat plain greek yogurt
2 tablespoons light mayonnaise
2 teaspoons Mustard powder
2 tablespoons Scallions, finely chopped
1/4 cup finely chopped celery
1/4 teaspoon Black pepper, freshly ground
1 each (12 oz can) solid white albacore tuna packed in water, drained
8 slices Hannaford Whole Wheat Double Fiber bread
2 medium tomatoes, thinly sliced
4 slices reduced-fat swiss cheese
1 spray olive oil cooking spray