Preheat oven to 300 degree F.
Spray a large tube pan or Bundt (12 cup capacity) with flour-added baking spray or grease with shortening or butter and dust with flour.
Sift the flour and whisk it together with the salt. Set aside.
In bowl of stand mixer fitted with a paddle, cream the butter, cream cheese and sugar on medium-high speed until light and fluffy, about 5 minutes. Be sure to stop and scrape the bowl often.
On medium speed, Add the eggs and the yolk one at a time, beating well after each addition and stopping to scrape the sides of the bowl.
Lower the mixer’s speed and add the flour mixture alternately with the cream, beginning and ending with the flour. Stir in the vanilla and zest (or more vanilla).
Transfer the batter to the prepared pan.
Put the cake in the 300 degrees F oven and bake for 75 to 90 minutes or until a cake tester inserted comes out with moist crumbs or the internal temperature registers around 205F.
Let cool in the pan for about 30 minutes, then carefully loosen from pan and turn onto a wire cooling rack to cool completely.
