In a large bowl, combine buttermilk, garlic powder, paprika, salt, and black pepper. Add chicken breasts, ensuring they are fully submerged. Cover and refrigerate for at least 1 hour or up to overnight for best results.

In a shallow dish, mix flour, breadcrumbs, and cayenne pepper (if using). Remove chicken from buttermilk and let excess drip off. Dredge each piece in the flour mixture, pressing lightly to adhere.

In a large skillet, heat about 1/2 inch of vegetable oil over medium-high heat. Once the oil is hot, carefully add the chicken breasts. Fry for about 5-7 minutes on each side or until golden brown and cooked through (internal temperature should reach 165°F). Remove chicken and place on paper towels to drain excess oil.

While the chicken is frying, prepare the garlic mayo by mixing mayonnaise, minced garlic, lemon juice, salt, and pepper in a small bowl.

To assemble the sandwiches, spread a generous amount of garlic mayo on the bottom half of each bun. Add a piece of crispy chicken, followed by lettuce and tomato slices. Top with the other half of the bun.

Serve immediately.