Ingredients

• 3 cups cake flour
• 1/2 teaspoon salt
• 1/4 teaspoon baking soda
• 1/2 pound (2 sticks) unsalted butter, at room temperature
• 3 cups granulated sugar
• 6 large eggs, separated, at room temperature
• 2 teaspoons vanilla extract
• 1 1/4 cups sour cream, at room temperature

Instructions

1. Position a rack in the center of the oven, and preheat to 350 degrees F. Lightly butter a 10-inch tube pan. Dust the pan with flour, and tap out the excess. I use the cake flour for dusting.
2. Sift together the flour, 1/4 teaspoon of the salt, and the baking soda.
3. In a large bowl, using a hand-held electric mixer set at high speed, beat the butter until creamy, about 1 minute.
4. Add the sugar and beat until light in color and texture, about 2 minutes.
5. Beat in the egg yolks, one at a time, beating well after each addition.
6. Add the vanilla extract. Reduce the speed to low, and in thirds, alternately beat in the flour mixture and sour cream.
7. In a large greaseproof bowl (I use glass), using a hand-held electric mixer (clean beaters) set at low speed and beat the egg whites until foamy.
8. Add the remaining 1/4 teaspoon salt, increase the speed to high, and beat until the whites just form stiff peaks.
9. Stir about one fourth of the beaten whites into the batter; then fold in the remaining whites.
10. Transfer the batter to the prepared cake pan, smoothing the top.
11. Bake until the cake is golden brown and a wooden pick or bamboo skewer inserted comes out clean, 1 1/4 to 1 1/2 hours.
12. Cool the cake completely on a wire rack.
13. Run a long knife around the edges to release the cake from the pan, then unmold.