Heat cast iron pan on low to medium heat. While that's heating, mix egg and half of the chopped spring onion.
1 egg, 1 spring onion / green onion
Place one sheet of rice paper in the pan and pour on the egg mix, spreading to the edges immediately with the back of a spoon. Rotate the pizza a few times with tongs to make sure it's not sticking.
1 Rice paper sheets
Break up the tuna and sprinkle over the pizza.
95 g tuna
Swirl as much mayonnaise and sriracha as you'd like on the top and leave the pizza to cook for an extra minute or two, rotating every now and then until nice and crispy. Sprinkle over with the remaining spring onion.
kewpie mayonnaise, sriracha, 1 spring onion / green onion
Serve by either cutting into slices OR - or a more authentic experience - fold the pizza in half / thirds and wrap in newspaper to eat by hand.