Thinly slice the onion and Cheongyang chili pepper.
Spread pizza sauce over the tortilla.
Drain the oil from the spicy tuna can and evenly spread the tuna over the tortilla.
Top with the sliced onion and Cheongyang chili pepper.
Generously add shredded mozzarella cheese on top.
Place the tortilla pizza on a heated pan, cover, and cook on low heat until the cheese melts.
Cut into bite-sized pieces and serve.