In a large bowl or stand mixer, mix butter, flour, brown sugar, and granulated sugar until well combined. Fold in the oats, macadamia nuts, and shredded coconut flakes.
Make sure the jam is warm, at room temperature, or cold so it spreads easily. Top the crust with a thick layer of the guava jam making sure it is evenly spread over the crust.
Allow to cool completely before slicing with a sharp knife. You may have to clean the knife as you go since the guava jam gets sticky. Serve for brunch or dessert. Enjoy!