Scrape the carrots and slice them into 1/4-inch thick rounds. Melt butter in a heavy saucepan and add carrots, onions, and nutmeg. When onions are lightly browned, pour in vinegar. Cook, covered, over low heat until carrots are tender.
Meanwhile, soak raisins in 1/2 cup warm water. When carrots are done, drain raisins and dump them into the saucepan along with the brown sugar. Stir gently until raisins are heated through. Serve steaming hot.