Move the oven rack to the lowest position (remove other racks). Heat oven to 350°F.
In an extra-large glass or metal bowl, beat cake mix and cold water on low speed of 30 seconds; beat on medium speed 1 minute. Pour into an ungreased 10-inch angel cake pan. Do not use a fluted cake pan or 9-inch angel food cake pan, or batter will overflow.
Bake for 35 to 45 minutes or until the top is dark golden brown and cracks feel very dry and not sticky. Do not underbake.
Immediately turn the pan upside down onto a glass bottle until the cake is completely cool, about 1 hour. Run knife around edges; remove from pan. Tear cake into about ¾-inch pieces.
Pour boiling water on gelatin in a large bowl; stir until gelatin is dissolved. Add raspberries (If desired), remove several berries and reserve for garnish). Refrigerate the gelatin mixture for about 15 minutes or until thickened but not set.
Layer half each of the cake pieces, yogurt, cool whip, gelatin mixture in a 3-quart glass bowl; repeat. Garnish with reserved berries. Refrigerate at least 2 hours until firm. Cover and refrigerate any remaining dessert.