Slice the eggplants lengthwise, keeping the slices attached at the stem. Fan them out by pressing down with your hands. Generously brush the eggplants, onion and zucchini with the mojo, reserving 1 tablespoon for the dressing. Grill or broil the vegetables for 20 minutes, or until the eggplant and zucchini are tender and the onion is charred and crisp-tender. Carefully peel the onion and cut it into 1-inch slices.