For the dulce de leche syrup: Preheat the oven to 425 degrees F. Scrape the condensed milk into an 8-inch baking dish and cover the top tightly with heavy-duty aluminum foil. Place the dish inside a roasting pan and fill the pan with enough water to come halfway up the sides of the baking dish. Bake in the oven until the milk turns a deep golden brown, stirring a few times, about 1 hour 15 minutes. Check after 45 minutes and add more water, if needed, to the roasting pan. Remove the dulce from the oven and let cool, covered, about 15 minutes before serving.
For the crepes: Melt 6 tablespoons butter in a small saucepan over medium heat until it turns a nutty brown color. Remove from the heat, whisk in the cinnamon and let cool slightly.
Put the flour and salt in a medium bowl. Whisk together the milk, water and eggs until combined. Add the egg mixture to the flour and whisk until just combined. Whisk in 4 tablespoons of the brown butter and reserve the remaining 2 tablespoons for the crepe pan. Cover with plastic wrap and refrigerate for at least 30 minutes and up to 24 hours.
Mash the remaining 6 tablespoons butter and the vanilla seeds with a mortar and pestle. In a saute pan over medium heat, add the vanilla butter, mangoes and papaya and cook until softened and slightly caramelized, 3 to 5 minutes.
Whip the heavy cream, sour cream and vanilla extract in a large bowl until soft peaks form. Cover and keep chilled until ready to use.
Heat an 8-inch or 10-inch nonstick pan over medium heat. Brush with some of the remaining brown butter. Add a scant 1/4 cup of the batter into the pan and swirl the pan to cover the bottom with a very thin coating. If there is excess batter, pour it back into the bowl. Cook until the crepe bubbles and the bottom is lightly browned, about 1 1/2 minutes. Flip the crepe over and cook for about 20 seconds. Slide the crepe onto a plate. Repeat with the remaining batter.
Put a line of fruit down the center of each crepe. Spread a little of the warm dulce de leche on top of the fruit and fold or roll the sides of the crepe over. Top with a dollop of whipped cream and sprinkle with cinnamon.