Preparing the Tuna Filling
In a bowl, combine 1 (5-ounce) can tuna (drained and flaked) with 1 tablespoon mayonnaise, 1 teaspoon lime juice, ¼ cup finely chopped red onion, ¼ cup finely chopped bell pepper, 1 small finely chopped jalapeño (optional, seeds removed), and 2 tablespoons chopped fresh cilantro. Season with salt and pepper to taste and mix until well combined.
Making the Zesty Lime Sauce
In a separate bowl, whisk together ½ cup plain Greek yogurt, ½ cup mayonnaise, the juice of 1 lime, 1 minced jalapeño pepper, 1 teaspoon minced capers, ½ teaspoon ground cayenne pepper, ½ teaspoon dried oregano, ½ teaspoon ground cumin, and ½ teaspoon dried dill until smooth and creamy. Refrigerate until ready to serve.
Assembling the Quesadillas
Lay out 4 flour tortillas (8-inch size) and spread the tuna mixture evenly over half of each tortilla. Sprinkle 1 cup shredded cheddar cheese (divided among tortillas) over the filling, then fold each tortilla in half to enclose.
Cooking the Quesadillas
Heat a skillet over medium heat and add 1 tablespoon butter (or use cooking spray). Cook the quesadillas one or two at a time for about 2–3 minutes per side, until the tortillas are golden brown and the cheese is melted.
Serving
Slice the quesadillas into wedges and serve hot with the zesty lime sauce on the side for dipping.
