Defrost the shrimp and microwave. Mix onion, tomato, shrimp, sriracha, ketchup, and pepper together.
Place the tortilla on a frying pan.
Put all the prepared ingredients on one half of the tortilla.
Add basil pesto and cheese.
Fold the tortilla in half and cook over low heat, flipping until both sides are cooked.
When the cheese melts and the quesadilla becomes crispy, enjoy!