Make the guava paste: Reserve 3 whole guavas for garnish. Process the rest in a blender with the sugar and the cinnamon until smooth. Pour into a heavy saucepan, passing the paste through a strainer to catch all the seed bits.
Cook the guava paste for 10 - 15 minutes until it thickens, cooking constantly and being careful because it might splatter. Remove from heat and let the paste cool. Measure 1 1/4 cup of the guava paste and reserve the rest for the glaze.
Make the Guava-Cheese cream and assemble the cake: In a large bowl, using a mixer, beat the softened cream cheese, condensed milk, 1 ΒΌ cup of guava paste, and lemon juice until smooth. In a 9" springform cake pan, arrange a layer of Maria cookies to form the base. Pour a layer of guava cream on top. Repeat the layers until the cake ring is almost full (3 more times) but leaving room at the top for the glaze. Refrigerate for 2 hours or until firm.
Make the guava glaze: Hydrate the unflavored gelatine with a little water and let it rest for 5 minutes. Then melt in the microwave and let it cool down. In the blender, combine the reserved guava paste and the melted unflavored gelatine and blend until smooth. Pour blended mixture into the springform pan, on top of the cake and refrigerate until firm. See notes.
When you are ready to serve, run a sharp knife along the edge of the springform pan and then carefully unmold the Guava Charlotte. Garnish with guava slices or with your favorite fruit. See notes. Serve and enjoy!