Cut the zucchini in half and slice it into 0.5cm pieces.
Slice the onion thinly.
Add cooking oil to a pan and stir-fry the onion first.
When the onion becomes translucent, add the zucchini and stir-fry.
When the zucchini is slightly cooked, add the tuna (drained of oil).
Season with salt and pepper.
When all ingredients are evenly cooked, transfer to a plate.