Tuna Salad

From FeelGoodFoodie.com

2/3 cup greek yogurt
1/4 cup lemon juice
2 tablespoon Dijon mustard
1/2 teaspoon black pepper
2 tablespoon dill or parsley chopped
4 5-ounce white albacore tuna in water drained
4 celery stalks minced
4 tablespoons red onion minced