Reinvent the ice cream sundae with this tangy pineapple-ginger sauce.
With a sharp knife, slice off top and bottom of pineapple. Holding fruit upright on cutting board, slice off peel in strips; reserve peel. Cut flesh into 8 wedges. Remove core; reserve. Refrigerate wedges until ready to serve.
Cut reserved peel and core into 1-inch pieces; place in a medium saucepan with ginger, sugar, and 4 cups water. Boil until reduced to 1 cup, 25 to 30 minutes. Strain, discarding solids; chill.
Slice wedges thinly crosswise. Divide frozen yogurt evenly between 6 bowls. Top with pineapple and chilled syrup. Serve immediately.
Mix leftover syrup with seltzer water for a refreshing drink, or drizzle over yogurt or pancakes.