1. Heat oven to 350º
2. In a 9 X13 pan, melt butter in oven. Remove pan from oven; turn pan so butter evenly coats bottom of pan.
3. Spread rhubarb evenly in pan.
4. Drizzle with honey and sugar.
5. In a large bowl, beat cake mix, water, oil an eggs with electric mixer on low speed 30 seconds. Beat on medium speed 2 minutes, scraping bowl occasionally.
6. Pour over rhubarb mixture.
7. Bake 50-57 minutes or until tests done.
8. Cool completly, about 1 hour.
9. In chilled medium bowl, beat whipping cream, powdered sugar and vanilla on high speed until soft peaks form.
10.Frost cake with whipped cream.
11. Store loosely covered in refrigerator.