1 cup cold unsalted butter (8oz), cut in 1/2-inch pieces
1 8oz package cold cream cheese, cut in 1-inch pieces
2 3/4 cups sugar
1 tsp. kosher salt
4 tsp. pure vanilla
3 cups shifted cake flour (may also use 2 1/2 cups plus 2 tablespoons all-purpose flour, but note that it won't be as fine as a finished product)
1. Let eggs stand at room temperature for 30 minutes. Generously butter and lightly flour two 8x4x2-inch loaf pans or one 10-inch tube pan. (I'd recommend using the flour and oil spray that you find with Pam). Using a stand mixer with the paddle attachment beat cold butter about 2 minutes on low speed, occasionally raising to moderately high speed for 5 seconds to dislodge butter from paddle.
2. Add cream cheese. Beat on low speed for 3 minutes with occasional short bursts on high speed to dislodge mixture from paddle. Beat butter and cream cheese mixture until waxy and well-blended. Still mixing on low, add the sugar in a slow continuous stream. (About 1 1/2 to 2 minutes.) Add salt. Continue creaming the mixture for 5 minutes, scraping the sides and bottom of bowl once halfway though. Increase speed to medium, continue mixing for 2 more minutes.
3. Add eggs, one at a time, beating 20-30 seconds after each addition or just until each egg is fully incorporated before adding the next egg. Scrape sides and bottom of bowl after first three eggs. Beat in vanilla with the last egg.
4. Gradually add about 2 1/2 cups of cake flour on low speed, mixing until just blended (about 1 to 1 1/2 minutes). Turn off mixer. Fold in remaining flour by hand with a rubber spatula, just until combined.
5. Turn batter into prepared pan(s). Shake pan(s) gently to distribute batter. Run a spatula in zigzag pattern through batter. Drop filled pan(s) from a height of about 6 inches onto kitchen counter to dislodge any large air pockets.
6. Place on center rack of a COLD oven. Turn oven setting to 300*F. Bake for 1 hour 15 minutes to 1 1/2 hours without opening the oven door for the first 1 hour 15 minutes. Bake 1 hour 45 minutes for tube pan. Test for doneness with a cake tester in center of cake or by listening for light bubbling sounds that soften and slow and cake approaches doneness.
7. Transfer to cooling rack. Cool 10 minutes before removing from pan(s). Cool completely before serving.