12 tablespoons (1 1/2 sticks) softened unsalted butter, plus more for pan
3 cups all-purpose flour, spooned and leveled
1 1/2 teaspoons baking soda
3/4 teaspoon salt
2 cups ripe fruit (such as whole berries, or fruit cut into 1/2-inch pieces)
1 cup granulated sugar
1/2 cup light brown sugar
2 large eggs
1 1/2 teaspoons pure vanilla extract
1 1/2 cups buttermilk
Edible flowers and powdered sugar, for garnish (optional)
Instructions
Arrange the rack in the center of the oven and preheat the oven to 350 degrees F. Butter a 12-cup Bundt pan.
In a large bowl, whisk together flour, baking soda and salt; transfer 1/4 cup of the flour mixture to a medium bowl. Toss the fruit with the reserved flour mixture.
Combine the butter, granulated sugar and brown sugar in the bowl of an electric mixer. Using the paddle attachment with the mixer on medium speed, beat the butter and sugars until smooth and pale, 5 to 8 minutes. Add the eggs, 1 at a time, until incorporated. Mix in the vanilla. With the mixer on low, alternately add the flour mixture and buttermilk, beginning and ending with the flour. Fold in the fruit. Spoon the batter into the prepared pan (it should be about 2/3 full).
Bake until the top is golden and a toothpick inserted in the center tests clean, about 1 1/2 hours. Let the cake cool in the pan 45 minutes. Run a sharp knife along the sides of the pan to loosen the cake. Invert the cake onto a serving plate.