Place the tempeh in a saucepan with just enough water to cover. Add the tamari soy sauce. Bring to a boil, reduce the heat, and cook about 5 minutes, turning the tempeh over once. The tempeh will plump up with moisture.
Remove the tempeh from the water. Drain and cut into 24 (1-inch cubes.)
Toss the tempeh into the peanut sauce. Let marinate while you prepare the pineapple and onion. This can be done the day ahead.
To prepare the pineapple, slice off the skin, following the curve of the pineapple, cutting deep enough so most of the “eyes” are trimmed away. With a paring knife or the tip of a vegetable peeler, pick out any “eyes” still poking out from the fruit.
Cut 1-inch pieces of the pineapple, not much bigger than the cubes of tempeh.
Peel the onion. Cut about the onion into 1-inch wedges, separating the layers.
Heat the grill to medium-high. Thread the skewers, alternating onion, pineapple and tempeh, beginning and ending with an onion slice. (see note)
Pour satay sauce over the kebabs. Grill the kebabs 18 to 20 minutes. Turn them occasionally, brushing with peanut sauce several times, as needed. There should be dark grill marks on the pineapple and tempeh.
Serve hot with steamed brown rise or quinoa and plenty of peanut satay sauce.