Beat butter and cream cheese at medium speed with an electric mixer until creamy; gradually add sugar, beating well. Add eggs, 1 at a time, beating until combined.
Combine flour and salt; gradually add to butter mixture, beating at low speed just until blended after each addition. Stir in vanilla. Pour batter into a greased and floured 10-inch Bundt pan.
Bake at 300° for 1 hour and 40 minutes or until a wooden pick inserted in center comes out clean. Cool in pan on a wire rack 10 to 15 minutes; remove from pan, and let cool completely on wire rack.