Make the tuna salad

• Drain the tuna and flake it into a bowl.
• Add the Greek yogurt, mayonnaise, mustard and lemon juice.
• Stir in the celery and red onion, then season with salt and pepper.

Fill the wrap

• Lay the tortilla flat and cover with the lettuce and tomato slices.
• Spoon the tuna salad over the vegetables.

Roll and serve

• Fold in the sides and roll the wrap tightly.
• Cut in half and serve.