1Grease 4 8" round baking pans. Line bottoms of pans with parchment paper, cut into 8" rounds. Grease in pans and set aside. Preheat oven to 350. Sift together and baking soda in a large mixing bowl and set aside.
2In a separate large bowl with an electric mixer at med. speed, cream butter and sugar until well-blended. Add vanilla, beat till combined. Pour in egg and egg white one at a time, beating 1 min. after each addition. With electric mixer on low speed blend in yogurt.
With electric mixer on low add dry, sifted ingredients and cold water, alternately to creamed mixture, stopping mixer occcasionally to scrape down sides of bowl. Mix till it is combined.
3Divide and pour batter evenly into 4 pans. Bake about 15 min, or until tester comes out clean.
Remove cakes from oven and cool 10 min on wire racks before removing from pans. Allow to cool completely, then carefully peel parchment paper off bottom of cakes before assembling.
4To assemble, plaze 1 cake round on cake plate and spread top with 1/3 cup of raspberry preserves. Top with second cake round and spread top with 1/3 cup of preserves. Top with 3rd cake and spread with rest of preserves. Top with 4th round and garnish with whipped topping and fresh raspberries.