2 × 185g cans tuna in springwater, drained

4 low-carb tortillas

4 tablespoons plain Greek yoghurt

1 teaspoon Dijon mustard

2 teaspoons lemon juice

2 celery stalks, finely diced

2 tablespoons finely diced red onion (optional)

2 tablespoon chopped parsley or coriander

Black pepper, to taste

Toppings

4 cups shredded lettuce

2 medium tomatoes, diced

1 avocado, smashed

Lemon or lime wedges, to serve