Preheat the oven to 325°F (163°C) and grease a 10-cup bundt pan well with nonstick cooking spray; set the pan aside.

In the bowl of a stand mixer (or a large bowl with a hand mixer), cream 1 cup salted butter (room temperature) and 3 cups granulated sugar together for 5–7 minutes, until light and fluffy.

Add 6 whole eggs (room temperature) one at a time, mixing well after each addition. Scrape down the sides and bottom of the bowl as needed.

Stir in 2 teaspoons vanilla extract, then beat the batter an additional 2 minutes until light and airy.

In a separate bowl, combine 3 cups all-purpose flour, 1/4 teaspoon baking soda, and 1/4 teaspoon salt.

Add half of the flour mixture to the batter and mix just until combined.

Add 1 cup sour cream and mix until incorporated.

Add the remaining flour mixture and mix just until the flour is incorporated. Scrape the sides and bottom of the bowl and finish folding/stirring the batter by hand with a spatula until completely smooth—avoid overmixing.

Pour the batter into the prepared bundt pan and smooth the top with a spatula.

Bake for 75–90 minutes, or until the cake is golden brown and a toothpick inserted near the center comes out clean or with just a few moist crumbs.

Let the cake cool in the pan on the counter for 15–20 minutes, until you can handle the pan while it is still warm. Invert the pan onto a cooling rack and remove the pan.

Once the cake is completely cooled, transfer it to a serving platter, dust with powdered sugar, and serve.