Preheat oven to 350 degrees. Butter and flour a 6-cup (8 1/2-by-4 1/2-inch) loaf pan; set aside.
Using an electric mixer on high speed, beat butter and sugar until light and fluffy. Add eggs one at a time, beating well after each addition; add vanilla and salt. With mixer on low, gradually add flour, beating just until combined (do not overmix).
Bake until a toothpick inserted in center of cake comes out clean, about 1 hour (tent with aluminum foil if browning too quickly). Let cool in pan 15 minutes. Invert onto a wire rack, and turn upright to cool completely.