Scrub and pierce sweet potatoes; place on a microwave-safe plate. Microwave, uncovered, on high for 12-14 minutes or until tender, turning once.
When cool enough to handle, cut a thin slice off the top of each potato and discard. Scoop out pulp, leaving a thin shell. In a large bowl, mash the pulp. Add the crushed pineapple, butter, salt, cinnamon, ginger, allspice and nutmeg; mix well. Spoon into sweet potato shells.
Place on a baking sheet. Sprinkle with pineapple tidbits and brown sugar. Bake, uncovered, at 325° for 30-35 minutes or until heated through. Yield: 8 servings.