Rhubarb is usually a spring thing…. but, here in the shade on Whidbey Island, my rhubarb usually ripens up right along with my later summer strawberries, and continues on right into late summer. Rhubarb pie and Strawberry Rhubarb Crisp are the standards when cooking with the vegetable, but this lovely Rhubarb Crumble Picnic Cake makes a nice addition to the Rhubarb Rotation!

This is a super easy, relatively quick dessert, that alway gets tons of appreciation from those who are lucky enough to get to taste it. Even those “reluctant rhubarb” folks will give positive reviews. It is a balanced rhubarb dessert, that isn’t overpowered by the tartness of the rhubarb. It has a buttery, cakey bottom topped by a layer of jammy rhubarb which is then topped off with a crumble layer. I sprinkle with powder sugar to finish it off and a pretty, finishing touch. Quite lovely.

Once baked and cooled, it is so easy to take this unique Rhubarb Crumble Picnic Cake to a picnic or party! Simply pull up on the parchment sling and transfer your cake to your cutting board. Cut your cake into roughly 2″ x 3″ pieces, which will give you 18 pieces. Arrange them nicely on a pretty tray, and watch them disappear once presented to your friends and family.

Ingredients

Rhubarb

1¼ Pound (565 grams) Rhubarb, cut into ½" diagonal pieces
2/3 Cup (128 grams) Granulated Sugar
1 Tbsp Fresh Lemon Juice Be sure to zest your lemon before juicing it, as you will need the zest to add to the cake batter.

Cake Layer

1/2 Cup (115 grams) Salted Butter, Softened
1 tsp Lemon Zest, Very Finely Grated
2 Large Eggs, Room Temperature
2/3 Cup (128 grams) Granulated Sugar
1⅓ Cup (165 grams) All Purpose (or Einkorn) Flour
1¼ tsp Baking Powder
3/4 tsp Salt
1/4 tsp Ground Ginger
1/3 Cup (80 grams) Sour Cream

Crumble

1 Cup (125 grams) All Purpose (or Einkorn) Flour
1/4 Cup (50 grams) Dark Brown Sugar
1/2 tsp Salt
1/4 tsp Ground Cinnamon
4 Tbsp (55 grams) Salted Butter, Melted
Powdered Sugar for Dusting

Instructions

Cake

Preheat oven to 350°. Prepare your 9 x 13 pan by spraying with non-stick spray, or generously buttering, bottom and sides. Line the pan, with parchment paper, taking care to leave about 4-5" of parchment overhanging on the long sides of the pan. This will create a "sling" for the cake so you can easily lift the finished cake out of the pan in order to cut it into serving sized pieces.
Prepare the Rhubarb by stirring the sugar and lemon juice into the cut rhubarb, taking care to coat all of the rhubarb. Set Aside.
Beat the Butter, Sugar, and Lemon Zest with a mixer until light and fluffy. Add Eggs, one at a time, taking care to scrape down the sides after each addition.
In a separate bowl, combine the Flour, Salt, Baking Powder, and Ginger. Whisk until combined.
Alternate adding the Flour Mixture and Sour Cream to your Egg/Sugar Mixture. Start with 1/3 or the Flour Mixture, gently mix until combined. Then add 1/2 Sour Cream, mix gently until combined. Continue with alternating additions, Flour-Sour Cream-Flour to finish it off. Gently mix until combined. Take care not to over mix, as over mixing = tough cakes.
Spoon batter over the parchment in the prepared pan. Using an offset spatula, smooth the batter out evenly in a thin layer.
Pour Rhubarb mixture over the batter, spreading it out evenly. It should make a nice, snug layer.

Crumble Topping

Stir together the Flour, Brown Sugar, Salt, and Cinnamon. Drizzle the melted butter over the dry ingredients, stir to combine.
Crumble the topping evenly over the Rhubarb layer.
Pop it in the oven. Bake for 55-60 minutes, until a toothpick inserted comes out clean, without wet dough from cake layer, and crumble top is golden brown.
Cool Completely in pan. Once cool, lift cake out of pan using the parchment "sling". Move to cutting board and sprinkle generously with powdered sugar. Cut into 2 x 3" pieces. Enjoy!

Rhubarb Crumble Picnic Cake