Melt butter and add both sugars and water(I drain the canned pineapple and use it for part of the water measurement). Boil. While waiting for first 4 ingedients to boil, arrange drained pineapple and drained canned yams into casserole pan. Pour boiled mix over pineapple and yams. Bake uncovered for 45 mins. Baste 2-3 times.