01 - Set a grill pan or large skillet over medium-high heat and allow it to come to temperature.
02 - Coat the chicken breasts evenly with olive oil, garlic powder, smoked paprika, salt, and black pepper. Place onto the hot grill pan and cook for 6 to 7 minutes per side until the internal temperature reaches 165°F and the juices run clear. Transfer to a plate and rest for 5 minutes before slicing thinly against the grain.
03 - In a mixing bowl, combine the shredded mozzarella, cheddar, grated Parmesan, minced garlic, mayonnaise, and chopped parsley. Stir until all ingredients are evenly incorporated into a cohesive spread.
04 - Lay each flour tortilla flat on a work surface. Divide the cheese mixture evenly among the four tortillas, spreading it across the center. Layer with baby spinach, sliced tomatoes, red onion if using, and the sliced chicken.
05 - Fold in the left and right sides of each tortilla toward the center, then roll tightly from the bottom up to form a secure wrap.
06 - Wipe the skillet clean and return it to medium heat. Place the wraps seam-side down and toast for 2 to 3 minutes per side until the exterior is golden brown and the cheese has fully melted inside.
07 - Slice each wrap in half on a diagonal and serve immediately while warm.