1. Prepare the Crust:

1. Preheat oven to 350°F (175°C). Place a 9-inch round baking dish inside a larger roasting pan.
2. In a saucepan over medium heat, combine sugar and water. Stir until sugar dissolves, then cook without stirring until caramel turns amber. Immediately pour into the baking dish, tilting to coat the bottom.
3. In a blender, combine pumpkin puree, condensed milk, evaporated milk, eggs, vanilla, cinnamon, nutmeg, and ginger. Blend until smooth.
4. Pour the pumpkin mixture over the caramel in the baking dish. Fill the roasting pan with hot water until it reaches halfway up the sides of the baking dish.
5. Bake for 50-60 minutes, or until the center is set. Remove from water bath and cool to room temperature, then refrigerate for at least 4 hours.
6. To serve, run a knife around the edges and invert onto a serving plate. The caramel will flow over the flan.