Arrange rhubarb evenly in a greased 13x9-in. baking dish. Combine sugar and gelatin powder; sprinkle over rhubarb. Sprinkle dry cake mix over gelatin mixture. Pour hot water over cake mix (do not stir). Top with coconut and almonds. Drizzle with butter.
Bake at 350° for 40-45 minutes or until a toothpick inserted in the center comes out clean. Cool on wire rack.