rhubarb_cake

A Grown-Up Crumble Cake

I have a lot of respect for the brave people who first tasted rhubarb in its raw and natural state and experimented until they finally rendered it edible. Its virtues are not immediately evident, with its poisonous leaves and sour stalks. Yet, once cooked with the required amount of sugar, this fruit (which is really a vegetable), will reveal a tart yet sweet flavor, both bold and mellow.  

Primarily grown in two forms, the early hothouse rhubarb has a signature reddish-pink color and the later field-grown variety features green to pale pink stalks and little variation in flavor. It first appears on farm stands in early May and is available until late summer. Frequently paired with strawberries to soften the acidity, the flavor really shines through when poached on its own in a simple sugar syrup and served over yogurt or ice cream or baked in pies and cakes. 


Rhubarb Oat Crumble Cake

If you are a rhubarb fan, it is worth growing your own. Once established, the plants are hardy and need little tending, though the crown will likely need a layer of mulch to protect it in the coldest months of winter. 

For June, I present a buttery lemon sponge with tart poached rhubarb and a sweet and crunchy oat topping, a cake that is sure to please both die-hard rhubarb fans and make new converts.

Step  1: Poached Rhubarb

This foolproof method ensures that the rhubarb retains its color and flavor and is not rendered into a mush. It is a great item to have on hand as a topping for yogurt or ice cream and any leftover syrup can be used to enhance summer cocktails. I sometimes add a sprig of rosemary or basil to the poaching liquid as it cools, or a hint of orange for extra flavor.

Ingredients

1 lb. rhubarb stalks (4 cups)
1 cup plus 3 Tbsp. sugar
1½ cups water
1 vanilla bean, split open, or 1/2 tsp. natural vanilla extract

Method

Trim the ends of the rhubarb stalks and cut into 2-inch batons. Place the sugar and water in a heavy saucepan and heat to dissolve the sugar. Bring the syrup to a boil and add the rhubarb pieces. Simmer for about one minute before removing the pan from the heat. Stir in the vanilla bean or extract and set aside until completely cool. The rhubarb will be perfectly cooked. Store in the refrigerator until ready to use.

Step 2: Oat Crumble

This crunchy oat crumble mixture can also be spread in a thin layer on a heavy sheet pan and baked at 365 degrees for 15-20 minutes, stirring to prevent sticking and burning. Cool and break into pieces. It makes an excellent topping for yogurt and fruit or eat by the handful as a sweet snack. Store and keep in an airtight jar for up to a week

Ingredients

1/3 cup unsalted butter softened
1/3 cup sugar
1 Tbsp. golden syrup or clear honey
1 cup rolled oats
½ cup whole wheat flour
¼ tsp. cinnamon
½ tsp. freshly grated nutmeg
1 tsp. fine sea salt
Pinch of baking powder

Method

Beat the butter and sugar and syrup with an electric mixer until light and fluffy. Place half a cup of the rolled oats into a blender or food processor and pulse until coarsely ground. Stir into a bowl with the rest of the oats, flour, spices, baking soda and salt. Add to the butter mixture and blend well. Mixture should be coarse and crumbly. Set aside while you make the cake batter.

Step 3: Cake Batter

Ingredients

1 cup unsalted butter, softened
1 cup sugar
4 eggs, lightly beaten
Finely grated zest of 1 small lemon
1 cup all-purpose flour
¼ cup almond flour
2 tsp. baking powder
½ tsp. fine sea salt

Method

Butter a 9×9 inch square baking tin and line with parchment paper. Mix the flour, baking powder, salt and almond flour and set aside. Cream the softened butter and sugar together with an electric mixer until light and creamy. Gradually add the eggs in several increments, making sure they are blended thoroughly before each addition. Add the lemon zest and flour mixture, beating on low speed. 

Pour the cake batter into the prepared tin. Remove the rhubarb from the syrup, using a slotted spoon to drain the juices. Cover the cake batter with a layer of the oat crumble, then arrange the rhubarb pieces on top before covering with the rest of the crumble. Place in the center of a preheated 390-degree oven and bake for about 45 minutes. Cover loosely with foil after about 30 minutes to prevent the top from browning too much. The top should be firm and lightly springy when the cake is done. Cook for a further five minutes if necessary. Cool in the tin on a wire rack. Once cool, flip over onto a large baking sheet, remove the tin and peel off paper and flip on to a large serving platter or tray. Place the remaining rhubarb juice in a small, heavy pan and simmer until thick, before cooling and storing in the refrigerator. Cut the cake into 12-16 pieces and serve with a little of the syrup drizzled over (optional).

This recipe works well with other fruit. You can substitute lightly poached apricots, sliced peaches or blackberries for the rhubarb. Feel free to experiment with your favorites.

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