Part 1: Prepare and Cook the Chicken

1. Dice the Chicken: If using chicken breasts or thighs that aren’t already cooked, dice them into small, bite-sized pieces (about 1/2-inch cubes). Uniformity in size ensures even cooking. Pat the chicken dry with paper towels; this helps it brown better.
2. Season the Chicken: In a medium bowl, combine the diced chicken with 1 tablespoon of olive oil, fresh lime juice, chili powder, cumin, smoked paprika, garlic powder, onion powder, dried oregano, salt, and black pepper. Toss thoroughly to ensure every piece of chicken is well-coated. For best results, you can let the chicken marinate for at least 15-20 minutes at room temperature, or up to 4 hours covered in the refrigerator. This allows the flavors to penetrate deeply.
3. Cook the Chicken: Heat the remaining 1 tablespoon of olive oil in a large skillet or frying pan over medium-high heat. Once the oil is shimmering, add the seasoned chicken to the hot pan. Spread it in a single layer and avoid overcrowding the pan (cook in batches if necessary). Cook for 5-7 minutes, stirring occasionally, until the chicken is cooked through and nicely browned on all sides. The internal temperature should reach 165°F (74°C).
4. Shred or Dice Further (Optional): Once cooked, remove the chicken from the skillet and let it rest for a few minutes. You can then either leave it as diced, or shred it with two forks if you prefer that texture in your quesadillas. For a finer filling, you can also give it a rough chop.
5. Sauté Vegetables (If Using): If you’re adding diced red onion and bell pepper, you can add them to the same skillet used for the chicken (add a touch more oil if needed). Sauté over medium heat for 3-5 minutes until slightly softened. Then, combine them with the cooked chicken.

Part 2: Assemble the Quesadillas

1. Prepare Your Workspace: Set up an assembly line. Have your cooked chicken mixture, shredded cheese, chopped cilantro (if using in the filling), and tortillas ready.
2. Combine Filling (Optional): In a bowl, you can mix the cooked chicken, sautéed vegetables (if used), and any optional add-ins like black beans, corn, or jalapeños, along with about half of the chopped cilantro. This ensures an even distribution of ingredients. Alternatively, you can layer them individually.
3. Layer the Quesadilla: Lay one tortilla flat on a clean surface.
   • Sprinkle about 1/4 to 1/3 cup of shredded cheese evenly over one half of the tortilla, leaving a small (about 1/2-inch) border around the edge.
   • Spread a layer of the chicken mixture (about 1/3 to 1/2 cup, depending on how full you like them) over the cheese.
   • Sprinkle another small layer of cheese (about 2-3 tablespoons) on top of the chicken. This top layer of cheese helps “glue” the tortilla halves together.
   • Fold the other half of the tortilla over the filling to create a half-moon shape. Gently press down.

   Alternatively, for a full-round quesadilla (often called a “sincronizada” in some regions): Sprinkle cheese over the entire surface of one tortilla. Top with the chicken mixture, then more cheese. Place a second tortilla on top and press gently. This method is great for larger appetites or when cutting into wedges for sharing.

Part 3: Cook the Quesadillas

1. Heat the Pan: Wipe out the skillet you used for the chicken (or use a clean large skillet, griddle, or comal). Place it over medium heat. Low to medium heat is key here – too high, and the tortilla will burn before the cheese melts.
2. Add Fat (Optional but Recommended): Once the pan is warm, you can either lightly brush the outside of the assembled quesadilla with melted butter or a very thin layer of oil, OR add about 1/2 teaspoon of butter or a drizzle of oil directly to the hot pan for each quesadilla. Butter adds flavor and helps achieve a beautiful golden-brown crust.
3. Cook the First Side: Carefully place the assembled quesadilla into the warm skillet. Cook for 2-4 minutes on the first side, or until the bottom is golden brown and crispy, and the cheese along the edges begins to melt. You can gently press down on the quesadilla with a spatula to help it cook evenly and ensure good contact with the pan.
4. Flip and Cook the Second Side: Carefully flip the quesadilla using a wide spatula. Cook for another 2-4 minutes on the second side, until it’s also golden brown and crispy, and the cheese inside is completely melted and gooey.
5. Rest and Cut: Remove the cooked quesadilla from the skillet and place it on a cutting board. Let it rest for a minute or two before cutting. This allows the cheese to set slightly, making it less messy to cut. Cut the half-moon quesadillas into 2 or 3 wedges. If you made a full-round quesadilla, cut it into 4 or 6 wedges, like a pizza.
6. Repeat: Repeat the cooking process with the remaining quesadillas, adding a little more butter or oil to the pan as needed for each one. Keep cooked quesadillas warm in a low oven (around 200°F or 90°C) on a baking sheet if you’re making a large batch, though they are best served immediately.