This is from Martha Stewart and it is quite an amazing tuna salad!
2 TBSP mayonnaise
1 TBSP fat-free Greek yogurt
1 tsp grated lemon zest
1 TBSP juice
Salt and pepper
1 can (5 oz) solid light tuna packed in water, drained and flaked
1 stalk celery, halved lengthwise and thinly sliced
1/2 Granny Smith apple, peeled and grated
Whole-wheat bread, red onion, cucumber, and alfalfa sprouts, for serving
Combine ingredients in a large bowl. Spoon onto bread and top with onions and cucumber.