Preheat oven to 350°.
Place butter and chocolate in a large microwave-safe bowl, and microwave at high 1 minute or until melted, stirring until smooth. Stir in sugar, water, and vanilla. Add egg whites and egg, stirring with a whisk. Lightly spoon flour into dry measuring cups, and level with a knife. Combine flour, baking powder, and salt, and add to chocolate mixture, stirring with a whisk until smooth. Coat bottom of a 13 x 9-inch baking pan with cooking spray; pour batter into pan. Bake at 350° for 30 minutes or until a wooden pick inserted in center comes out clean. Cool cake in pan on a wire rack. Serve cake with Coconut-Pecan Sauce.