Drain pineapple. Add water to pineapple syrup to make 1¼ c.
Combine cornstarch and ¼ c. brown sugar in saucepan. Add lemon juice and pineapple syrup mixture; cook, stirring constantly, until mixture is thick and clear. Remove from heat and add 2 tblsp. butter, stirring until it melts. Add pineapple.