For the cake:
1 cup (2 sticks) of unsalted butter, softened
2/3 cup packed light brown sugar
2/3 cup white sugar
4 large eggs, room temperature
1 tsp. baking soda
2 tsp. baking powder
1/2 tsp. cinnamon
1/2 tsp salt
2 cups flour (I used unbleached white; I don’t think whole grain would do well here, but I imagine a gluten-free blend would work nicely)
One 15-oz. can of unsweetened pumpkin, or 1 3/4 cups pumpkin puree
For the sauce:
1 cup packed light brown sugar
1/2 cup (1 stick) of unsalted butter
1 1/2 cups heavy cream
1/3 cup Lyle’s Golden Syrup (British, but my local supermarket carries it nowadays, as do many US grocery stores) or light corn syrup
Heat the oven to 350 degrees, and butter a 13 x 9 x 2 baking dish. Beat the butter and sugars together till fluffy, and then add the eggs one at a time – don’t worry if things start looking curdle-y at this point. Scrape down the bowl, and measure in the baking soda, baking powder, salt and cinnamon. Add 1 cup of flour and half the pumpkin, and mix well. Add the rest of the flour and pumpkin, and mix until smooth, scraping the sides of the bowl as necessary. Pour into the prepared pan and bake just until set – about 30 – 35 minutes.
While the cake bakes, prepare the sauce. Melt the butter and brown sugar in heavy bottomed saucepan with room for the cream to boil – at least 2 quarts. Whisk in the cream and syrup, bring to a boil, and cook, whisking, until the sauce reduced and thickened – about 8 minutes. Keep warm.
When the cake is done, remove it from the oven and poke it all over with a meat fork – the kind with 2 big prongs – if you have one, or a regular fork if you don’t. Pour about 1 cup of the warm syrup over the cake, and put the rest out with the cake, for diners to pour over their servings. Eat while it’s still warm with whipped cream or vanilla ice cream – or just as is.