To make the sauce, combine the ingredients for the sauce in a pot and whisk well. Cook on the stove on medium heat for 8-10 minutes, whisking often until the sauce thickens. Remove from the heat and set aside.

Combine the burger mixture by mixing the chicken, onion, garlic, coconut flour, salt, and pepper. Form into 4 burgers and set aside.

Prepare an outdoor grill, or a cast iron grill pan by greasing. Place the burgers onto the grill or grill pan, either in batches, or spread apart to not crowd the pan. Cook for 4-5 minutes on each side and carefully flip. Cook until internal temperature reads 165 F. Set aside.

Lightly clean the cooking surface and add more oil if needed. Add the pineapple slices and grill for 1-2 minutes on each side to add grill marks and to lightly soften.

Set aside and repeat grilling with the red onion for 2-3 minutes on each side. Set aside.

To assemble the burgers, layer each patty on top of a lettuce leaf top with half of the sweet and sour sauce, then top with pineapple, red onion, and finish with the remainder of the sauce. Top with green onion.