For the angel food cake: Preheat the oven to 325 degrees F.
Place the sugar in a food processor and process for 2 minutes, until very fine.
In a bowl, sift together the cake flour, salt and half of the fine sugar. Set aside.
Combine the egg whites, warm water, cream of tartar and vanilla in large bowl. Whisk by hand for 2 minutes, until well combined. At this point, switch to a stand mixer fitted with the whisk attachment. Beat the egg white mixture until medium peaks form, gradually adding the remaining fine sugar.
Sprinkle one-third of the flour mixture over the egg white mixture and gently stir it in. Repeat until all of the flour mixture has been evenly incorporated.
Spoon the cake batter into an ungreased 9-by-13-inch baking dish. Bake until the cake is golden brown and cooked through, 30 minutes.
Invert the baking dish onto a wire rack. Let the cake cool completely in the dish upside down. Once cooled, carefully scrape the edges of the baking dish to release the cake.
For the strawberry reduction: Combine the quartered strawberries, water and sugar in a small saucepan over low heat. Bring to a simmer and cook, stirring, for 5 minutes. Raise the heat to medium and cook, stirring occasionally, until the sauces thickens, about 10 minutes. Remove from the heat and allow to cool completely.
For the whipped cream: Place a metal mixing bowl and a metal whisk in the freezer for 10 to 15 minutes. Place the sugar in the mixing bowl, then add the whipping cream and vanilla. Whisk until the cream just reaches stiff peaks.
To assemble: Slice the cake horizontally into two equal layers. Place the first cake layer on a cake board. Pour over a thin layer of strawberry reduction and then add a layer of whipped cream. Stack the second cake layer on top.
Top off the cake with swirls of whipped cream, using a piping bag fitted with a No.1M large tip. Add a strawberry slice to each swirl.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.