I haven't had this but have been told that it is GOOOOOOD!
about 4 cups cut up rhubarb
1 C sugar
1 large box red Jello (any flavor)
white or yellow cake mix (prepared)
1 10oz bag miniature marshmallows
Line a 9' X 13" cake pan with parchment paper. Cover bottom of pan with a layer of cut up rhubarb. Sprinkle with 1 cup sugar, lightly with cinnamon, jello, miniature marshmallows, and prepared cake mix & bake according to directions on cake mix box. When completely cool, turn cake upside down on plate. It's very good served with Cool Whip or ice cream.