In a bowl, combine buttermilk, paprika, garlic powder, onion powder, salt, and black pepper. Add the chicken breasts, ensuring they are fully submerged. Cover and refrigerate for at least 1 hour, or overnight for best results.
In a shallow dish, mix together flour, breadcrumbs, and baking powder. Remove chicken from the buttermilk and let excess drip off. Dredge each piece in the flour mixture, pressing lightly to adhere.
In a large skillet, heat about ½ inch of vegetable oil over medium-high heat until shimmering. Carefully add the chicken breasts and fry for 5-7 minutes on each side, or until golden brown and cooked through (internal temperature should reach 165°F). Remove and drain on paper towels.
While the chicken is frying, prepare the garlic mayo by mixing mayonnaise, minced garlic, and lemon juice in a small bowl. Set aside.
To assemble the sandwiches, spread a generous amount of garlic mayo on the bottom half of each bun. Place a piece of fried chicken on top, followed by a slice of tomato and a piece of lettuce. Top with the other half of the bun.