Put butter in large oblong pan, add rhubarb, add marshmallows. Mix Jello and sugar, sprinkle on ... and egg with cake mix, pour over top of ... minutes. May serve warm.
Cover greased 9 x 13 pan with miniature marshmallows. Mix rhubarb, sugar and Jell-O. Let stand while preparing cake mix according to package directions. ... degrees for 45 minutes.