Drain pineapple juice into a small bowl; add teriyaki sauce.
Place 3 Tablespoon in a resealable plastic bag. Add
pineapple and rotate to coat; set aside. Shape beef into
four patties; place in a 8" square baking dish. Pour the
remaining teriyaki sauce mixture over patties; marinate for
5-10 minutes, turning once. In a skillet, saut onion in
butter until tender, about 5 minutes. Grill or broil burgers
until no long pink. Place pineapple on grill or under
broiler to heat through. Layer lettuce and onion on bottom
of buns. Top with burgers, cheese, pineapple and bacon.
Replace tops; serve immediately.
