Preheat oven to 350 degrees. Grease and flour two 9x2 inch round cake pans. Alternatively, you may use three.
In a large mixing bowl, beat sugar and butter at medium speed with an electric mixer until fluffy. Add strawberry extract, vanilla extract, pureed strawberries, and sour cream. Beat until combined.
Sift together flour, baking powder, soda, and salt. Gradually add to butter mixture, beating until combined.
Beat egg whites until stiff peaks form. Gently fold into batter.
Pour batter evenly into prepared pans. Bake for 30-35 minutes or until a wooden toothpick inserted in the center comes out clean.
Let cool in pans for 10 minutes then turn out onto wire racks. Cool completely.
To make frosting, beat butter and cream cheese for about 2 minutes. Add powdered sugar 1 cup at a time. Add jam and slowly add pureed strawberries. Taste test it at this point and add a little strawberry extract if you feel like it.
This icing is kind of soft, so I recommend putting the cake in the refrigerator as soon as you've finished frosting it. I stored mine in the refrigerator in a cake carrier. It tasted even better on Day 2.