Heat the grill to medium-high and line a baking tray with foil.
Place the chicken between 2 sheets of cling film and bash to an even thickness using a rolling pin.
Rub the spice mix, the oil and some seasoning all over the chicken, then put them on the baking tray.
Grill for 10 mins, turning halfway through. Top each chicken breast with a pineapple ring and some grated lactose free cheese, then return to the grill and cook for a further 2-3 mins until the cheese is golden and bubbling, and the chicken is cooked through.
Spread a little mayo over the base of each gluten free bun, then add lettuce, a chicken breast and pop the top on.