Preheat oven to 350°F degrees. Set a kettle of water to boil. Place an 8- or 9-inch cake pan with 2-inch high sides inside of a larger baking pan (such as a 13x9).
In a medium sauce pan over low heat, melt sugar until completely dissolved. Watch carefully so it does not burn. You may swirl the pan to stir. Remove from heat when it is a dark golden, amber color.
Immediately pour the melted sugar into the bottom of the cake pan. Working quickly before it hardens, tilt the pan to coat the bottom. Caution: pan will get hot. Place pan back in larger baking dish.
In a blender beat the cream cheese, sweetened condensed milk, evaporated milk, pumpkin, eggs, vanilla, cinnamon and nutmeg. Mix until well combined.
Strain the custard through a fine-mesh sieve to ensure there are no lumps and to remove excess air bubbles. Pour the strained custard into the cake pan over the sugar caramel.
Next, add boiling water to the larger pan until it reaches halfway up the sides of the cake pan. Bake for 60-75 minutes, or until the flan is set around the edges with a slight jiggle in the very middle.
Remove from oven and let the flan cool in the water bath, about an hour. Once cool, cover and refrigerate until thoroughly chilled. Overnight is best.
When ready to serve, run a knife around the edges to loosen. Set a plate over the flan and flip upside-down to invert. If desired, garnish with cinnamon sticks and pumpkin seeds. Slice into wedges and serve.