Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans, then line the bottoms with parchment paper. Set aside.

In a large bowl, whisk together the sifted flour, granulated sugar, baking powder, and salt. Make a well in the center.

In a separate medium bowl, whisk together the whole milk, room temperature eggs, and vanilla extract.

Add the softened butter to the dry ingredients in the large bowl. Pour about half of the wet ingredients over the butter and dry mixture. Beat with an electric mixer on low speed until just combined. Scrape down the sides of the bowl.

Gradually add the remaining wet ingredients, mixing on medium speed until the batter is smooth and well combined, but do not overmix. Overmixing can lead to a tough cake.

Divide the batter evenly between the two prepared cake pans. Smooth the tops with a spatula.

Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean. The cakes should be lightly golden and spring back when gently pressed. (You might need to rotate them halfway through baking for even browning).

Let the cakes cool in their pans on a wire rack for 10-15 minutes before inverting them onto the wire rack to cool completely. Remove parchment paper. Ensure cakes are completely cool before assembling, about 1-2 hours.

In a medium saucepan, whisk together the guava nectar, granulated sugar, and cornstarch until smooth.

Place the saucepan over medium heat and cook, stirring constantly with a whisk, until the mixture thickens and comes to a boil. It should be thick enough to coat the back of a spoon.

Remove from heat. Stir in the fresh lime juice and the cold butter pieces until the butter is fully melted and incorporated.

Transfer the guava filling to a heatproof bowl. Press a piece of plastic wrap directly onto the surface of the filling to prevent a skin from forming. Chill in the refrigerator for at least 1 hour, or until firm and cold.

In a large mixing bowl, using an electric mixer, beat the softened cream cheese and softened butter together on medium speed until smooth and creamy, about 2-3 minutes. Make sure there are no lumps of cream cheese.

Gradually add the sifted powdered sugar, 1 cup at a time, mixing on low speed until combined. Once all sugar is added, increase speed to medium-high and beat for another 2-3 minutes until the frosting is light, fluffy, and smooth.

Stir in the vanilla extract and pinch of salt. Beat for a final 30 seconds to incorporate.

Once the cakes are completely cool, use a serrated knife to level the tops of the cakes if necessary, creating flat surfaces.

Place one cake layer on your serving plate or cake stand. Spread the chilled guava filling evenly over the top, leaving a small border (about 1/2 inch) around the edge.

Carefully place the second cake layer on top of the guava filling. Gently press down to secure.

Using an offset spatula or butter knife, spread a thin layer of cream cheese frosting over the top and sides of the entire cake (this is your crumb coat). Chill the cake in the refrigerator for 15-20 minutes to set the crumb coat.

Once the crumb coat is set, apply the remaining cream cheese frosting evenly over the top and sides of the cake. Create decorative swirls or smooth the frosting as desired.

If desired, garnish the top with toasted coconut flakes and fresh guava slices before serving.