This is perhaps the most delicious cake I've ever made and I don't even really like pumpkin all that much. I encourage you to make it. The best thing about this cake is that it keeps really well - like for days and days. I made this cake on Tuesday night and it was just perfect for Thanksgiving and lasted (barely) until Monday when it was still awesome and moist.
When I went to make this cake I discovered, much to my dismay, that my buttermilk had gone bad. This was really quite irritating because I'd bought it on Sunday and the expiration date was the 25th of November, also known as tomorrow. I was very annoyed. Looking back on it though I think if it hadn't had the orange fuzzy dots in it (gross) I probably would have thrown out perfectly good buttermilk - because it is supposed to be very chunky. My advice: give it a good shake to distribute everything and try to ignore the sound it makes as it splats into the measuring cup.
Pumpkin Spice Cake with Buttermilk Icing
Adopted from Gourmet (via Epicurious)
1 1/2 sticks (3/4 cup) unsalted butter, softened, plus additional for greasing pan
2 1/4 cups all-purpose flour plus additional for dusting pan
2 teaspoons baking powder
1 teaspoon baking soda
1 teaspoon cinnamon (Mine was a heaping teaspoon...I love cinnamon)
3/4 teaspoon ground allspice
1/2 teaspoon salt
1 1/4 cups canned solid-pack pumpkin (a 15-ounce can is more than enough; not pie filling)
3/4 cup well-shaken buttermilk
1 teaspoon vanilla
1 1/4 cups granulated sugar
3 large eggs
(I think you could probably get away with making half of this recipe - I had a ton of extra)
2 tablespoons plus 2 teaspoons well-shaken buttermilk
1 1/2 cups confectioners sugar
Put oven rack in middle position and preheat oven to 350°F. Butter pan* generously, then dust with flour, knocking out excess.
Whisk together flour, baking powder, baking soda, cinnamon, allspice, and salt in a bowl. Whisk together pumpkin, buttermilk, and vanilla in another bowl.
Beat butter (1 1/2 sticks) and granulated sugar with a fork in a large bowl until pale and fluffy, then add eggs one at a time and stir to incorporate after each egg. Add flour and pumpkin mixtures alternately in batches, beginning and ending with flour mixture and mixing until batter is just smooth.
Spoon batter into pan, smoothing top, then bake until a wooden pick or skewer inserted in center of cake comes out clean, 45 to 50 minutes. Cool cake in pan on a rack 15 minutes, then invert rack over cake and reinvert cake onto rack. Cool 10 minutes more.
While cake is cooling, whisk together buttermilk and confectioners sugar until smooth. Drizzle icing over warm cake, then cool cake completely. Icing will harden slightly. (I actually didn't drizzle until the next day, I heated up the cake a bit and drizzled and it was just fine - it wasn't a hard icing but it was still delicious.)
*The original recipe is made in a bundt pan but I don't have one (and Brad so kindly talked me out of buying a $12 pan I clearly don't need) so I used a springform pan and it worked great. I think these would also make excellent muffins.