Frosting: Using electric mixer, beat cream cheese and butter in a large bowl until smooth, stopping to scrape down sides of bowl. Beat in sugar and jam. Beat cream in medium bowl until peaks form. Fold whipped cream into frosting. Cover, and chill until firm enough to spread (about 2 hours)
Cake: Preheat oven to 325. Butter and flour two 9-inch cake pans with 2 inch high sides. Sift flour, salt, baking powder, and baking soda into medium bowl. Using electric mixer beat sugar and butter until fluffy. Add eggs 1 at a time, beating to blend after each addition. Beat in vanilla. Add sour cream, beat 30 seconds. Add flour mixture in three additions, beating to blend in between each addition. Divide batter between prepared pans. Bake cakes until tester inserted comes out clean, about 50 minutes. Cool in pans on rack about 10 minutes. Run small sharp knife around pan sides, then turn out cakes onto racks and cool completely. Using a large serrated knife, cut each cake horizontally in half. Place one cake half cut side up on cake plate. Spread 2 tablespoons of strawberry jam over, then 3/4 cups frosting. Top with 3/4 cup sliced berries, arranging in a single layer. Repeat two more times with cake layer, jam, frosting and berries, Top with remaining cake layer cut side down. Spread 2 cups frosting over top and sides of cake to coat completely. Spread remaining frosting over top and sides of cake. Stir remaining 1/3 cup jam to loosen. Spoon teaspoonfuls on to top and sides of cake, then use back of spoon to swirl jam decoratively into frosting. Can be made 8 hours ahead. Cover with cake dome and refrigerate.
* You may add a few drops of red food coloring to make the frosting pinker. Also omit the jam swirled into frosting on the outside of cake.