Rhubarb Upside-Down Cake

Back in August when I was making other rhubarb-based treats, I made this cake and it was really good.  Cutting and placing the rhubarb made for a pretty design--though I obviously could've crammed more together in the center of the cake pan.  I based the recipe off this Real Simple one, but I made some changes.    

Ingredients: 

• 1 1/4 cups unsalted butter, room temperature
• 1 1/2 cup white sugar, divided
• 2 cups flour (cake or all-purpose)
• 1/2 tsp. salt
• 1 tsp. vanilla
• 1/3 cup plain yogurt (I used greek yogurt)
• 1 lb. rhubarb, cleaned and cut (I did about 1 inch sticks with diagonal ends)
• 1/2 cup packed brown sugar
• 1 1/4 tsp. baking powder
• 1/2 tsp. dried lemon peel (or 1 tsp. fresh zest)
• 4 large eggs, room temperature
• Cinnamon sugar, optional

Directions:

1. Preheat oven to 325°F.
2. Grease a round cake pan, line bottom with parchment, and grease parchment.
3. Stir rhubarb with 1/2 cup of white sugar and 1/4 cup of brown sugar.
4. Layer rhubarb in bottom of pan and add the remaining sugar mixture to it.  I made concentric circles!
5. Whisk flour, baking powder, and salt together.  
6. In a separate bowl beat the butter, the rest of the white and brown sugar, and lemon zest with mixer until light and fluffy, about 4 minutes.
7. Scrape down the sides of the bowl, then beat in vanilla and eggs, one at a time. 
8. Stir in yogurt at a low speed (the original recipe said, "The mixture may look curdled.")
9. Gradually add flour mixture and stir to combine. 
10. Spoon batter over rhubarb and smooth top evenly.
11. Sprinkle cinnamon sugar on top.  
12. Bake until toothpick comes out clean, about 1 hour and 15 minutes.
    
13. Cool for 15 minutes or so, then remove from pan, upside down on a plate.  Take off the parchment carefully and serve warm (or cold).  Store in the fridge.