Preheat the oven to 325 degrees . Position the oven rack to the middle. Place 8 six-ounce ramekins into a large pan that’s at least 2 inches deep (a very large roasting pan usually works). Bring a kettle of water to a simmer.
Mix all the caramel ingredients together in a 4 cup microwave-safe glass measuring cup. Place in microwave for between 4 to 5 minutes until it's a medium brown, caramel color. Remove and let sit for 5 minutes to finish cooking. It will darken slightly while the bubbles subside. Divide equally between the eight ramekins. Let cool until the caramel hardens before pouring the flan mixture in.
In a small pot, heat the milk and sugar together over low heat just until the sugar has dissolved. Cool slightly. Combine the condensed milk, guava puree and cream cheese in a blender jar and process until smooth. In a large bowl, whisk the eggs until thoroughly blended. Stir in the cooled milk mixture and the guava mixture, taking care not to create too many bubbles. Ladle the flan into the ramekins over the hardened caramel.
Open the oven and pull out the oven rack. Carefully place the roasting pan on the rack, then slowly pour the simmering water around the ramekins, filling it to a depth of about 1 inch. Slowly slide the rack into the oven. Bake until the flans are barely set in the middle, between 45 to 50 minutes. Remove from the oven and let cool in the water bath, about 1 hour. Refrigerate until thoroughly chilled, about 2 hours.
Run a small knife around the edge of each of the flans to release them from the sides of the mold. Lay a small serving plate over one of the ramekins, grasp the plate and ramekin firmly, then reverse the two. Gently shake it up and down until you hear the flan drop onto the plate. Remove the ramekin. Repeat with the remaining flans. Scrape any remaining caramel out of the molds and onto the flans.