Peel the vegetables. Cut the avocado in two, remove the pit, then cut into slices and squeeze some lemon juice on top to prevent browning.
Cut the tomatoes in half and then slice. Finely mince the red onion. Finely chop the coriander.
Spread each tortilla with mayonnaise, then top with some white tuna, avocado slices, red onion, tomato and coriander. Sprinkle with a bit of salt.
Roll up each tortilla closed, holding the garnishes in place, wrap them in plastic film and place in the refrigerator. To serve, remove the film, cut the wraps in two diagonally and roll the uncut ends in aluminium foil to hold them closed and make them easier to hold onto.
Make guacamole from mashed avocado, lime and a pinch of ground cumin, and spread it on the tortilla before the other ingredients.