1. Prepare the Crust:

1. Preheat oven to 350°F (175°C). Place a 9-inch round baking dish or flan mold inside a larger roasting pan.
2. Make the caramel: In a medium saucepan over medium heat, melt the 1 cup of granulated sugar, stirring constantly until it becomes a deep amber liquid. Immediately pour the hot caramel into the baking dish, carefully tilting to coat the bottom evenly. Set aside to harden.
3. Make the custard: In a blender, combine the sweetened condensed milk, evaporated milk, pumpkin puree, eggs, vanilla extract, cinnamon, nutmeg, and ginger. Blend until the mixture is completely smooth.
4. Pour the custard mixture over the hardened caramel in the baking dish.
5. Create a water bath: Carefully pour hot water into the larger roasting pan until it reaches about halfway up the sides of the flan dish.
6. Bake for 50-60 minutes, or until the center is just set but still slightly jiggly. Carefully remove the flan from the water bath and let it cool to room temperature. Then, refrigerate for at least 4 hours, or preferably overnight.
7. To serve, run a thin knife around the edge of the dish. Place a serving plate upside down over the dish and quickly invert it. The flan will release onto the plate with the caramel sauce flowing over the top.