Heat oven to 350°F. Grease and flour 13x9-inch pan. In large bowl, combine cake mix, water, oil and eggs; beat at low speed until moistened. Beat 2 minutes at high speed. Pour into greased and floured pan.
Top batter evenly with rhubarb. Sprinkle with sugar. Pour cream over top.
Bake at 350°F. for 1 1/4 to 1 1/2 hours or until toothpick inserted in center comes out clean. Cool 30 minutes before serving. Store in refrigerator.