Preheat oven to 325°F. Grease bottom and sides of a 9-inch loaf pan. Line bottom and long sides of pan with parchment, leaving about an inch of overhang on both sides. Grease and flour paper and pan, tapping out excess.
Sift flour and salt together into a small bowl. Set aside. Put butter, vanilla and sugar in bowl of an electric mixer and beat on medium speed until light and pale, 3 to 5 minutes. Add eggs one at a time, beating well and then scraping bowl between each.
With mixer on low, add flour to mixture gradually until it is fully incorporated; do not overmix. Pour batter into prepared pan and smooth top with a spatula. Bake until a toothpick inserted in center of cake comes out clean, about 1 hour and 15 minutes.
Cool cake on a wire rack for 15 minutes. Run a knife along unlined sides of pan and use parchment to carefully lift cake onto wire rack to cool completely. Serve with whipped cream and berries, if desired.