Rhubarb Crumb Cake
Adapted from Baked Explorations
Aside from adding rhubarb, I used a vanilla bean in the batter and added some extract to the crumb, omitted the cinnamon, subbed in more dark brown sugar, subbed in some oats for flour, and browned the butter for the crumb. To ensure large chunks of crumb, I put the mixture in the refrigerator to rest while I made the cake batter.
Makes 1, 9×13 inch, cake.
For the crumb topping:
1 1/2 cups firmly packed dark brown sugar
1/2 teaspoon salt
1 cup (2 sticks) unsalted butter, browned
1 teaspoon vanilla extract
2 cups all-purpose flour
1 cup rolled oats
For the batter:
2 1/2 cups all-purpose flour
3/4 teaspoon baking powder
1 teaspoon baking soda
1/2 teaspoon salt
12 tablespoons (1 1/2 sticks) unsalted butter, softened
1 vanilla bean, split and scraped (or 2 teaspoons vanilla extract)
1 cup granulated sugar
1/2 cup dark brown sugar
2 large eggs
1 1/4 cups sour cream
1 1/2 heaping cups rhubarb cut into 1/2 inch pieces (I would do as much as 3 cups in the future)
Preheat the oven to 350ºF. Line a 9×13 inch baking pan with parchment, leaving an overhang on 2 sides, and grease well.
Make the crumb in a mixing bowl by stirring together the sugars, salt, and flour. Fold in the browned butter and press the crumb firmly into the bowl before placing in the refrigerator to rest while you prepare the batter.
In another bowl, combine the flour, baking soda, baking powder, and salt for the batter. Place the rhubarb pieces in another bowl and toss with about 1 tablespoon of the dry mix, just to coat lightly. Set aside.
In the bowl of a mixer, beat the butter until smooth. Add the sugars and the scrapings from the vanilla bean. Beat until the mixture begins to lighten in color and become a bit fluffy. Add the eggs one at a time, beating well and scraping the bowl after each addition. Add the sour cream and beat until just combined. Add the dry ingredients in 3 parts, scraping down the bowl after each addition and beating until just combined. Scrape the batter into the prepared cake pan and smooth the top. Scatter the rhubarb over the top of the batter. Grab handfuls of the crumb topping, squishing it in your fist to make large chunks of crumb, and cover the entire cake. Bake the cake for 45-60 minutes (mine took the full 60) or until a toothpick inserted in the center comes out clean. Remove from the oven and cool on a rack for at least 30 minutes before cutting and serving. Leftover cake can be wrapped well in plastic and stored at room temperature, though I opted to refrigerate the wrapped leftovers. Serve any leftover cake at room temperature.