Cream butter and sugar until light and fluffy. Add eggs one at the time on low speed. Sift cake flour with soda and salt. Alternate adding dries and sour cream. Scraping down between additions. Be careful not to over mix once the flour has been added. Add vanilla. Heavily grease tube pan and dust with flour. Pour in mixture. Place in a cold oven and turn the temperature to 325 degrees Fahrenheit. Bake for 1 hour and 30 minutes, or until cake tester come out clean. Don't open the oven door prior to one hour.