Preheat oven to 350ºF. Grease and flour 10-inch cake pan and set aside.
Sift together flour and baking powder in a small mixing bowl.
Place egg yolks and ½ cup sugar in bowl of standing mixer with wire whisk. Whip on high speed to thick, light ribbon stage.
Remove from mixer, pour liquid into large mixing bowl and set aside. Clean bowl of standing mixer.
Place egg whites in bowl of standing mixer with wire whisk and beat until foamy. Add cream of tartar and remaining ½ cup sugar. Whip on medium speed until whites are glossy and stiff, but not dry.
Remove bowl from mixer and fold ⅓ of egg whites into whipped egg yolks. Repeat until all egg whites are incorporated.
Sprinkle ⅓ of sifted flour over batter and fold in. Repeat until all flour is incorporated. Pour into prepared cake pan and bake until golden brown and spongy, about 30 minutes.
Remove cake form oven and place pan on wire rack. Soak with syrup while cake is warm, repeating until cake is thoroughly saturated.
Ice cooled cake with whipped cream. Sprinkle with coconut and drizzle guava paste. Refrigerate until ready to serve.
Mix all ingredients in medium bowl.
Place guava paste in bowl of standing mixture fitted with paddle attachment. Beat on low speed to break down guava paste, increasing speed if necessary. Slowly add warm water until sauce is thin enough to drizzle.