Step 1

Place 2 sticks of the unsalted butter in the bowl of a stand mixer (or large bowl if using an electric hand mixer). Place 6 large eggs and 1 cup sour cream on the counter. Let everything sit at room temperature until the butter is softened, 1 to 1 1/2 hours.

Step 2

About 30 minutes before the butter is ready, arrange a rack in the middle of the oven and heat the oven to 325℉.

Step 3

Place the remaining 1 tablespoon unsalted butter in a small microwave-safe bowl and microwave until melted, 20 to 30 seconds. Add 1 tablespoon of the all-purpose flour and mix to form a smooth paste. Brush the paste on the inside of a 10-cup Bundt cake pan, making sure to thoroughly coat the tube and all the crevices.

Step 4

Place the remaining 3 cups all-purpose flour and 1/4 teaspoon baking soda in a medium bowl and whisk to combine.

Step 5

Add 2 1/2 cups granulated sugar and 1 teaspoon kosher salt to the butter. Beat with the paddle attachment on medium speed until lightened in color and fluffy, using a flexible spatula to scrape down the sides of the bowl as needed, 4 to 5 minutes total. Beat in 2 teaspoons vanilla extract and the eggs one at a time, beating well and scraping down the sides after each addition.

Step 6

Add half of the flour mixture and beat on the lowest speed until just combined. Add the sour cream and beat until just combined. Add the remaining flour and beat until the batter is smooth and combined, scraping down the sides as needed.

Step 7

Transfer the batter into the Bundt pan and smooth out the top. Pick up the pan and gently tap on the work surface a few times to remove any air bubbles.

Step 8

Bake until the top is golden-brown and a toothpick inserted in the center comes out clean, 65 to 75 minutes. Place on a wire rack and let cool for 30 minutes in the pan. Invert the cake out of the pan and onto the rack. Let cool completely, at least 2 hours.

Step 9

Place some powdered sugar in a fine-mesh strainer and dust it over the top of the cake before slicing and serving.