1/2 can frozen guava (or guava/strawberry) juice concentrate
3 tablespoons corn starch, mixed with enough water to make a smooth paste.
Heat oven to 350 degrees.
Coat 3 9” cake pans, or 2 pans plus a few cupcake holders, generously with baking spray. Cut circle of parchment paper, add to pan, then spray well again.
Mix cake flour, baking powder, salt & baking soda in a medium bowl. Set aside.
Beat butter, sugar and vanilla in large bowl with an electric mixer until fluffy. Beat in eggs, one at a time, on medium speed. Alternate flour mixture and milk, beating until well blended, scraping bowl occasionally then continue to beat 2 minutes longer.
Spread batter evenly into prepared pans.
Bake 20 to 25 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes then remove from pans and put onto a wire rack to cool completely.
Beat cream cheese, butter & vanilla in medium bowl with electric mixer on medium speed, until well combined. Gradually add powdered sugar. Add milk by teaspoonfuls until frosting reaches desired spreading consistency.
In small pan, add guava concentrate on medium heat. When thawed, slowly add corn starch mixture, and whisk until smooth. Keep on low heat until thickened. Take off burner & let cool then place in the refrigerator to completely cool before frosting the cake.
Place 1 cake layer on a serving plate. Spread and cover the cake layer with part of the frosting. Continue with additional layers, then frost top & sides. Put 1/2 cup frosting in pastry bag and pipe an edge around top of cake, or build up an edge with a spoon. Set cake in refrigerator for 10 minutes. When cool, add some of the Guava Sauce to the top. Spread evenly. Add more or less, to your liking. Drizzle some down the sides if you want. Save the extra Guava Sauce for topping cut slices if desired.