1-Pound the chicken: Place breasts between plastic wrap and pound to an even 1/2‑inch thickness.

2-Make the marinade: Whisk olive oil, lemon juice, minced garlic, rosemary, thyme, oregano, salt, pepper, and smoked paprika if using. Pour over chicken, coating well. Marinate at least 30 minutes at room temperature or refrigerate up to 24 hours.

3-Preheat the grill: Heat a gas or charcoal grill to medium‑high (400‑450°F). For a grill pan, preheat thoroughly and lightly oil the grates.

4-Grill the chicken: Remove chicken from marinade, letting excess drip off. Grill 6‑7 minutes per side, flipping only once, until internal temperature reaches 165°F. Add cheese slices during the last minute and close the lid to melt.

5-Rest the chicken: Transfer to a cutting board and let rest for 5 minutes to lock in juices.

6-Toast the buns: Place split buns cut‑side down on the grill for 1 minute until lightly golden.

7-Mix the garlic mayo: Stir together 1/2 cup mayo, 1 finely grated garlic clove, and 1 teaspoon lemon zest. Let sit while you slice the chicken so flavors meld.

8-Assemble the sandwiches: Spread garlic mayo on both toasted bun halves. Layer arugula, sliced tomato, red onion, and rested chicken (sliced or whole). Close up and serve immediately.