Do not preheat the oven. Butter and flour a large (10-12-cup) Bundt or tube pan. You can set the pan on a foil-covered baking sheet in case of any over-flow. (If your pan is the correct size, overflow should not be an issue.)
Sift together the flour and salt on a piece of parchment paper and set aside.
Beat butter and cream cheese at medium-high speed of electric mixer until blended and creamy, about 8 minutes. Gradually add sugar, beating another 5-7 minutes on medium. The batter should get very fluffy and pale yellow, with no discernible lumps of cream cheese.
Add eggs, one at a time, mixing on low just until yellow disappears. Scrape the sides of the bowl after 3 eggs.
With mixer on low, slowly pour in the flour from the parchment paper. Beat on low speed just until blended. Be sure to scrape the sides and bottom of bowl to blend every bit. Add vanilla and stir or mix just until blended.
Pour batter into the prepared pan and place in cold oven along with a 2 cup oven-proof measuring cup or bowl filled with water.
Bake at 300 degrees F for about 1 hour and 15-30 minutes or until a cake tester inserted in center comes out with just a few moist crumbs. Start checking at about 1 hour and 15 minutes.
Let cake cool in pan on wire rack for 15 minutes then flip onto wire rack.
