Grease and flour a 10x5x3-inch loaf pan. Line bottom with parchment paper. With rack in center, heat oven to 325 degrees. Place a baking sheet on the rack to heat. Sift together flour, salt and baking powder. In an electric mixer with paddle attachment, beat butter on medium speed until light and fluffy, 3 to 4 minutes. Gradually add sugar; beat until creamy. Beat in eggs one at a time. Add vanilla; beat until creamy. With mixer on lowest speed, gradually add flour mixture. Mix just until incorporated. Scrape batter into prepared pan; tap on countertop to settle. Place pan on baking sheet in oven. Bake at 1 hour to 1 hour and 15 minutes, until cake is golden on top and a tester inserted into center comes out clean. Let pan cool on a rack for 1 hour. Slide knife around cake to loosen. Invert pan to remove cake, then place upright on rack. When completely cool, wrap tightly in plastic and let stand 24 hours. Serve with fresh mixed berries on the side.