Begin by marinating the chicken. In a bowl, combine buttermilk, garlic powder, onion powder, salt, black pepper, and lemon zest. Add the chicken breasts, ensuring they are fully submerged. Cover and refrigerate for at least 1 hour or up to overnight for best flavor.

In a separate bowl, mix together the flour, baking powder, and lemon pepper seasoning. Remove the chicken from the marinade and allow any excess buttermilk to drip off. Dredge each piece of chicken in the flour mixture, pressing lightly to ensure an even coating.

In a large skillet, heat about 1 inch of vegetable oil over medium-high heat until it reaches 350°F. Carefully add the coated chicken breasts to the hot oil, cooking in batches if necessary to avoid overcrowding. Fry for 5-7 minutes on each side or until golden brown and cooked through (internal temperature should reach 165°F).

Once cooked, transfer the chicken to a paper towel-lined plate to drain excess oil.

To assemble the sandwiches, place a piece of crispy chicken on the bottom half of each bun. Top with lettuce, tomato slices, and a dollop of mayonnaise if desired. Place the top half of the bun on each sandwich.

Serve immediately and enjoy your crispy lemon pepper chicken sandwiches!