Ingredients
Unsalted butter, softened, for pans
1 3/4 cups cake flour (not self-rising)
1 1/4 cups sugar
1 3/4 teaspoons baking powder
3/4 teaspoon kosher salt
1/3 cup safflower oil
6 large egg yolks, plus 8 large whites, room temperature
2/3 cup whole milk, room temperature
2 teaspoons lemon zest, plus 2 tablespoons fresh juice
1 vanilla bean, split and seeds scraped
1/4 teaspoon cream of tartar
3 cups heavy cream
1 cup plus 2 tablespoons sugar
1/4 teaspoon kosher salt
1 tablespoon pure vanilla extract
2 cups fresh blackberries, plus more for serving
Seasonal fruit, such as Seckel pears, figs, plums, and Concord grapes, for serving
Preparation
Cake: Preheat oven to 325F°. Butter two 9-inch round cake pans. Line with parchment; butter parchment. In a large bowl, whisk together flour, 3/4 cup sugar, baking powder, and salt. In another bowl, whisk together oil, egg yolks, milk, lemon zest, and vanilla seeds. Whisk yolk mixture into flour mixture.
Beat egg whites on high speed until frothy. Add cream of tartar and beat until soft peaks form, about 2 minutes. Gradually add remaining 1/2 cup sugar, beating until stiff, glossy peaks form, about 5 minutes. Whisk one-third of mixture into batter. With a rubber spatula, gently fold in remaining egg white mixture.
Divide batter evenly between prepared pans. Bake until golden and tops spring back when lightly touched, about 30 minutes. Transfer pans to a wire rack; let cool 10 minutes. Turn cakes out upside-down onto rack and let cool completely.
Fruit and Whipped Cream Layers: In a medium saucepan over medium-high heat, bring berries, 2 tablespoons sugar, lemon juice, and 2 tablespoons water to a boil. Reduce heat and simmer 5 minutes, stirring occasionally and breaking up berries with the back of a spoon. Pass mixture through a fine-mesh sieve, pressing on solids to release all juices. Let cool completely.
Combine heavy cream, remaining 1 cup sugar, salt, and vanilla in the bowl of a mixer fitted with the whisk attachment. Beat on low speed until sugar has dissolved, about 1 minute. Increase speed to medium-high and beat to firm peaks, about 3 minutes more.
To Assemble: With a serrated knife, trim tops of cake layers to level; split each in half horizontally to form a total of 4 layers. Place one layer, bottom-side down, on a serving platter. Spread 1 1/2 cups whipped cream evenly over top. Repeat process with remaining cake layers, spreading 1 1/2 cups whipped cream between each layer and leaving top layer uncovered. (For stability, insert a wooden dowel or skewer into center of cake, trimmed so dowel is just shorter than top of cake.)
Spread remaining 1 1/2 cups whipped cream over top of cake in decorative swirls. Garnish with fruit, scattering it on top of cake and around perimeter of platter. Drizzle with blackberry coulis and serve immediately.
