Blueberry Crumb Cake

Ingredients

• 1 tablespoon (12.5 grams) granulated sugar
• 1 1/2 cups (250 grams) fresh or frozen blueberries
• 2 teaspoons lemon juice
• 1 teaspoon finely grated lemon zest
• 1/8 teaspoon salt
• 1 teaspoon pure vanilla extract
• 1/2 cup granulated sugar
• 1/4 cup dark brown sugar
• 1 teaspoon ground cinnamon
• 1/2 teaspoon table salt (OR 3/4 teaspoon kosher salt)
• 10 tablespoons (141 grams) salted or unsalted butter, melted and still warm
• 2 1/4 cups (270 grams) cake flour (see note below for substitution)
• 1 3/4 cup (210 grams) all-purpose flour
• 2 tablespoons (14 grams) cornstarch
• 3/4 cup (150 grams) granulated sugar
• 1/2 teaspoon baking soda
• 1/2 teaspoon salt
• 9 tablespoons salted or unsalted butter cut into 9 pieces, at room temperature
• 2 large eggs + 1 large egg yolk, at room temperature
• 1/2 cup buttermilk, at room temperature
• 2 teaspoons pure vanilla extract

Instructions

1. 1

   Add all the blueberry swirl ingredients except the...: Add all the blueberry swirl ingredients except the vanilla extract to a small saucepan and heat over medium heat, smashing some of the berries against the side or bottom of the pan with a fork or pastry cutter.

2. 2

   Bring the mixture to a boil and continue...: Bring the mixture to a boil and continue to cook over medium heat, stirring frequently, for 10-15 minutes, until the mixture is thickened. If you drip some onto a plate, the blueberry sauce should hold its shape. (If using frozen blueberries this might take a few extra minutes.)

3. 3

   Remove the pan from the heat and stir...: Remove the pan from the heat and stir in the vanilla. Scoop into a bowl and allow to cool completely before using. (The blueberry sauce will keep in the refrigerator for up to 4 days.)

4. 4

   Add both sugars, cinnamon, salt, and melted butter...: Add both sugars, cinnamon, salt, and melted butter to a medium size bowl and whisk vigorously to combine.

5. 5

   Add the flour to the butter and sugar...: Add the flour to the butter and sugar mixture. Using your hands or a rubber spatula, rub the flour into the butter until completely moistened. Cover and set aside.

6. 6

   Preheat your oven to 325 degrees F (163...: Preheat your oven to 325 degrees F (163 degrees C). Prepare a 9 or 10-inch springform pan as follows: Coat the inside with vegetable shortening or butter, fit the bottom of the pan with a round of parchment paper and coat the top of the paper with more vegetable shortening or butter. Shake some flour around inside the greased pan until the sides and bottom of the pan are coated. Shake out the excess flour and set aside. (More about how to prepare cake pans so the cake won't stick.)

7. 7

   Add the flour, cornstarch, sugar, baking soda, and...: Add the flour, cornstarch, sugar, baking soda, and salt to the bowl of an electric mixer fitted with the paddle attachment. Mix on low just to combine.

8. 8

   With the mixer running on medium-low speed, add...: With the mixer running on medium-low speed, add the butter, piece by piece, mixing until the butter is completely incorporated into the flour and the mixture looks like coarse crumbs.

9. 9

   Add the eggs and egg yolk, buttermilk, and...: Add the eggs and egg yolk, buttermilk, and vanilla and beat on medium speed for 1 minute to combine.

10. 10

    Scoop the batter into the prepared springform pan...: Scoop the batter into the prepared springform pan and smooth it into an even layer. Drop spoonfuls of blueberry sauce all over the top of the cake batter. With a butter knife, swirl the blueberry sauce into the cake batter. Sprinkle the crumb topping over the top of the cake, squeezing it in your hands as you do to create large pieces of crumb.

11. 11

    Bake the cake for 60-70 minutes. The cake...: Bake the cake for 60-70 minutes. The cake is done when a toothpick inserted in the center comes out without any raw batter on it.

12. 12

    Remove the cake from the oven and allow...: Remove the cake from the oven and allow it to cool on a wire rack for at least 15 minutes before removing the sides of the springform pan. Serve warm or at room temperature. The cake will keep in an airtight container at room temperature for up to 2 days.