Preheat oven to 350°F. Grease a 9x13-inch pan.
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
In a large bowl, beat the egg whites and cream of tartar until soft peaks form. Set aside.
In a large bowl, beat egg yolks and sugar at medium speed until the mixtures thickens and becomes pale. Slowly add the water and the vanilla and coconut extracts. Beat until well combined. Scrape the sides of the bowl as needed. Stir in the flour mixture. Gently fold in the egg whites. Pour mixture into the prepared pan, smooth the top with an offset spatula.
Bake for 30 minutes or until a toothpick inserted in the middle of the cake comes out clean. Remove from oven and place on a cooling rack. Cool to room temperature.
Prepare the soak by combining all the ingredients. Run a knife around the edges of the cake to loosen from pan. Poke the cake all over with a toothpick or fork. Slowly, pour the entire soak mixture over the cake. Be patient as it may take time for all the liquid to absorb. Cover and refrigerate for at least 4 hours or overnight.
When ready to serve, whip the cream with the sugar and extracts until medium peaks form. Spread all over the cake and decorate by swirling the cream with a spoon or a spatula. Sprinkle toasted coconut on top.