1 stick (4 ounces) unsalted butter, cut into pieces
Three 15-ounce cans unsweetened pumpkin puree
6 large eggs, separated
6 tablespoons unsalted butter, melted
2 teaspoons finely grated orange zest
1 1/2 cups cake flour
2 tablespoons baking powder
3/4 teaspoon cinnamon
3/4 teaspoon freshly grated nutmeg
3/4 teaspoon salt
1/4 cup plus 2 tablespoons sugar
In a small saucepan, combine the sugar, corn syrup, and water. Simmer over moderate heat, stirring once or twice, until a deep amber caramel forms, about 15 minutes. Add the cream and butter and stir over moderate heat until the caramel is smooth, about 3 minutes. Pour the caramel into a heatproof bowl and set aside to cool.
Preheat the oven to 375°. Arrange 2 racks in the center part of the oven. Butter and sugar twenty 1/2-cup ramekins and place them on 2 large baking sheets.
In a food processor, combine the caramel with the pumpkin puree, egg yolks, melted butter, and orange zest. Process until smooth and transfer to a large bowl.
In a large bowl, sift the cake flour with the baking powder, cinnamon, nutmeg, and salt. Whisk to combine, then fold the flour into the pumpkin-caramel mixture until blended.
In a large stainless steel bowl, beat the egg whites until soft peaks form. Add the sugar and beat until firm peaks form. Gently fold the egg whites into the pumpkin batter until only a few streaks of white remain. Spoon a rounded 1/2 cup of the batter into each prepared ramekin. Bake the cakes for about 30 minutes, until they are risen and set. Carefully unmold the hot pudding cakes onto dessert plates and serve at once.
The pumpkin caramel cakes can be baked and refrigerated for up to 1 day in their ramekins. Reheat the cakes in a 400° oven for about 10 minutes, or until warmed through, then unmold and serve immediately.