lemon rhubarb pie cake

This is based on a recipe for a rhubarb upside-down cake from the New York Times. My recipe is considerably better though.

2 lemons worth of zest
1/2 cup lemon juice

1 1/2 cup flour
1 tsp baking powder
1/4 tsp salt

1 stick of butter
1 cup sugar
1/2 tsp vanilla
3 eggs
1/2 cup buttermilk

3 lbs rhubarb (about 8 cups)
4 tbs cornstarch
1 cup sugar

1 stick butter
1 cup brown sugar

1/4 cup lemon juce
1/4 cup sugar

1. preheat oven to 325
2. line the bottom of a 9” springform pan with parchment paper, cover sides and bottom with butter
3. mix zest and juice
4. mix flour, baking powder and salt
5. beat butter until soft
6. add sugar and vanilla and mix well
7. add eggs one at a time mixing well in between
8. add half the dry ingredients, mix
9. add the buttermilk, mix
10.add the rest of the dry ingredients, mix
11. add the juice and rind, mix
12. chop up the rhubarb
13. mix the rhubarb with the cornstarch and the sugar
14. mix brown sugar and butter in a pan over medium heat for about 2 minutes
15. pour the brown sugar mixture into the pan
16. spoon the rhubarb into the pan
17. pour on the batter
18. bake for about 1 hour and 15 minutes
19. after it is in the oven mix the lemon juice with the sugar
20. mix it periodically while the cake is baking to dissolve the sugar
21. once the cake is done let it cool for 15 minutes
22. while it is cooling, cover the top (that will ultimately be the bottom) with the juice and sugar mixture so that it can soak in
23. run a knife around the edge, put a plate on top and flip the cake
24. release the cake from the pan while it is still a bit warm or it will stick
25. serve with an ample amount of freshly whipped cream