For Cake:.

Heat oven to 350°F; coat bottom (not sides, bottom only) of a 9x13 baking pan with cooking spray.

Beat egg whites with 1 tablespoon water, cream of tartar, and salt in a bowl with an electric mixer on medium low speed until foamy.

Continue to beat, adding sugar a little at a time, until batter is fluffy.

Add vanilla and beat about 1 minute more. Sprinkle a small amount of flour over top of batter and fold into batter. Repeat 8-10 times or until you've added all the flour.

Spread batter evenly in pan, using spatula to even out corners (shake pan once or twice to even surface).

Bake until cake is a light golden color and surface springs back gently to the touch. (25-30 minutes).

Run a sharp knife around edges of cake to separate from pan.

Cook for 2 hours.

For Filling:.

Heat berry preserves in a small pan over medium heat, stirring constantly, until it reaches a gentle simmer.

For Frosting:.

Melt chocolate in a double boiler.

Take bowl off heat and stir in sour cream.

Assembly:.

Place a cutting board over cake pan and invert cake onto board.

With a biscuit cutter or round cookie cutter, cut 12 rounds from cake.

Top 6 rounds with 1 heaping tablespoon of raspberry filling then place remaining cake rounds on top.

Spread 1/4 cup frosting over top and sides.

Top with raspberries.

Can serve immediately or refrigerate and bring to room temp about 1 hour before serving.