In a blender combine the sauce ingredients and process until smooth. Season with salt and pepper. Transfer to a small serving bowl. Set aside at room temperature until ready to serve.
In a large bowl whisk the marinade ingredients, including 1 teaspoon salt and freshly ground black pepper. Remove the small, tough side muscle that might be left on each scallop. Add the scallops to the marinade and turn to coat evenly. Cover and marinate at room temperature for 15 to 20 minutes while the grill preheats. Note: If the scallops are large, you may want to cut them in half.
Prepare the grill for direct cooking over high heat (450° to 550°F).
In a medium bowl combine the cabbage and onion.
Brush the cooking grates clean. Lift the scallops one at a time from the marinade, letting the excess marinade drip back into the bowl. Discard the marinade. Grill the scallops over direct high heat, with the lid closed as much as possible, until lightly browned and just opaque in the center, 4 to 6 minutes, turning once or twice. Remove from the grill.
Warm the tortillas over direct high heat for about 10 seconds on each side.
Fill each tortilla with some of the cabbage mixture and three scallops. Top with the sauce. Best if served immediately.