1-Pound the chicken: Place chicken breasts between plastic wrap and pound to an even ½-inch thickness to prevent dry edges and uneven cooking.

2-Make the marinade: Whisk together olive oil, lemon juice, minced garlic, thyme, parsley, salt, and pepper.

3-Marinate the chicken: Add chicken to marinade, turning to coat. Let sit at room temperature for at least 15 minutes, or refrigerate up to 4 hours (overnight for deepest flavor).

4-Whip up garlic mayo: Stir together mayonnaise, grated garlic, and lemon zest. Refrigerate to meld flavors while you grill.

5-Preheat the grill: Heat outdoor grill to medium-high (375-400°F) or use a grill pan/cast iron skillet indoors. Lightly oil the grates.

6-Grill the chicken: Cook 5-6 minutes per side until internal temperature reaches 165°F at the thickest part. Do not press with a spatula to avoid squeezing out moisture.

7-Rest the chicken: Transfer to a plate and let rest for 5 minutes so juices redistribute and meat stays moist.

8-Toast the buns: Lightly toast brioche or ciabatta buns on the grill or in a toaster to prevent sogginess.

9-Assemble the sandwich: Spread garlic mayo on both bun halves. Layer lettuce, tomato, and red onion on the bottom bun, add warm sliced chicken, and close with the top bun.