Marbled Blueberry Bundt Cake
- 3 cups (15 ounces) all-purpose flour
- 1 1/2 teaspoons baking powder
- 3/4 teaspoon baking soda
- 1 teaspoon salt
- 1/2 teaspoon ground cinnamon
- 3/4 cup buttermilk
- 2 teaspoons grated lemon zest plus 3 tablespoons juice
- 2 teaspoons vanilla extract
- 3 large eggs plus 1 large yolk, room temperature
- 18 tablespoons (2 1/4 sticks) unsalted butter, softened
- 2 cups (14 ounces) sugar
- 3/4 cup (5 1/4 ounces) sugar
- 3 tablespoons low- or no-sugar-needed fruit pectin
- Pinch salt
- 10 ounces (2 cups) fresh or thawed frozen blueberries
- 1 teaspoon grated lemon zest plus 1 tablespoons juice
1. FOR THE CAKE: Adjust oven rack to lower-middle position and heat oven to 325 degrees. Heavily spray 12-cup nonstick Bundt pan with baking spray with flour. Whisk flour, baking powder, baking soda, salt, and cinnamon together in large bowl. Whisk buttermilk, lemon zest and juice, and vanilla together in medium bowl. Gently whisk eggs and yolk to combine in third bowl.
2. Using stand mixer fitted with paddle, beat butter and sugar on medium-high speed until pale and fluffy, about 3 minutes, scraping down bowl as needed. Reduce speed to medium and beat in half of eggs until incorporated, about 15 seconds. Repeat with remaining eggs, scraping down bowl after incorporating. Reduce speed to low and add one-third of flour mixture, followed by half of buttermilk mixture, mixing until just incorporated after each addition, about 5 seconds. Repeat using half of remaining flour mixture and all of remaining buttermilk mixture. Scrape down bowl, add remaining flour mixture, and mix at medium-low speed until batter is thoroughly combined, about 15 seconds. Remove bowl from mixer and fold batter once or twice with rubber spatula to incorporate any remaining flour. Cover bowl with plastic wrap and set aside while preparing filling (batter will inflate a bit).
3. FOR THE FILLING: Whisk sugar, pectin, and salt together in small saucepan. Process blueberries in blender until mostly smooth, about 1 minute. Transfer 1/4 cup puree and lemon zest to saucepan with sugar mixture and stir to thoroughly combine. Heat sugar-blueberry mixture over medium heat until just simmering, about 3 minutes, stirring frequently to dissolve sugar and pectin. Transfer mixture to medium bowl and let cool for 5 minutes. Add remaining puree and lemon juice to cooled mixture and whisk to combine. Let sit until slightly set, about 8 minutes.
4. Spoon half of batter into prepared pan and smooth top. Using back of spoon, create 1/2-inch-deep channel in center of batter. Spoon half of filling into channel. Using butter knife or small offset spatula, thoroughly swirl filling into batter (there should be no large pockets of filling remaining). Repeat swirling step with remaining batter and filling.
5. Bake until top is golden brown and skewer inserted in center comes out with no crumbs attached, 60 to 70 minutes. Let cake cool in pan on wire rack for 10 minutes, then invert cake directly onto wire rack. Let cake cool for at least 3 hours before serving.
Properly swirling the thickened blueberry puree is key to producing an elegantly marbled cake.
1. After spooning half of batter into Bundt pan, make channel with back of spoon.
2. Using spoon, fill channel with half of blueberry filling in even layer.
3. Using butter knife, swirl filling through batter. Repeat these steps with remaining batter and filling