Soak kitchen twine in a small bowl with water. Set aside. Preheat your grill to 350° F.
Lay pineapple on its side. Cut off and discard the leafy crown from the top and a small portion from the bottom of the fruit to create a flat surface.
Stand the pineapple up on a cutting surface and slice down next to the core on each of the four sides to create 4 "planks". Cut and store pineapple in refrigerator for another use.
Rinse salmon under cold water and pat dry with paper towel. Lay a few sprigs of cilantro on top of a pineapple plank, then A salmon filet and brush with teriyaki sauce. Add another sprig of cilantro and top with another pineapple plank. Secure with kitchen twine tightly so salmon doesn't slide out when grilling. Repeat with other salmon and pineapple.
Grill covered for 15 minutes and turn over, then cut kitchen twine. Remove pineapple plank and set on outer area of grill to continue to cook and caramelize. Baste top of each salmon with teriyaki sauce several times. Cover the grill and cook for a few more minutes until the salmon springs back when pressed slightly and is opaque.
Remove from grill and allow to rest 5 minutes. To plate, serve each grilled salmon on top of one of the grilled pineapple planks, baste one more time with any remaining teriyaki sauce and garnish with a sprinkle of sesame seeds. Cut remaining grilled pineapple from planks and serve with steamed rice.