1Heat oven to 325°F. In a large mixing bowl, combine the calabaza, butter, and spices. Turn onto a baking sheet and cook until the calabaza is fork tender, about 20 minutes.
2Purée the calabaza mixture and set aside. (If using the canned pumpkin, combine all the ingredients in a mixing bowl and set aside.)
For the flan base:
1Whisk the egg yolks and eggs together until frothy; set aside. In a large heavy-bottomed saucepan over medium heat, combine the cream, milk, sugar, scraped vanilla beans, vanilla pod and salt and bring to a boil.
2Temper by whisking a portion of the cream mixture into the beaten eggs. Add the combined mixture back into the boiled cream and whisk thoroughly.
3Add the calabaza mixture and whisk to combine. Prepare an ice water bath by filling a bowl halfway with ice and water. Strain mixture through a fine mesh sieve and cool over ice water bath.
For the caramel:
1Combine sugar, lemon juice, and 1 cup water in a medium saucepot over medium heat. With a wet pastry brush, wipe down the sides of the saucepan.
2Cook the caramel until it achieves an amber color. Remove from heat immediately.
1Preheat oven to 300°F. Set a medium pot of water over high heat to boil.
2Pour the caramel into 1/2-cup or 1-cup ramekins and immediately pour the caramel out so the cups are lined with caramel.
3Let the caramel harden in the ramekins, then fill the ramekins to three-quarters height with the flan.
4Create a water bath by putting the ramekins into a glass baking dish and then adding enough of the boiling water to two-thirds height of the ramekins.
5Cover the flan and bake until the flan sets (i.e., it will not jiggle), about 45 minutes. Serve in the cups with whipped cream.