Forget that butter cake recipe I posted recently. Here's another recipe from America's Test Kitchen.

Buttermilk Spice Cake

1 tablespoon ground cinnamon
3/4 teaspoon ground cardamom
1/2 teaspoon allspice
1/2 teaspoon cloves
1/4 teaspoon ground nutmeg

Combine the spices and reserve 1/2 teaspoon.

4 tablespoons unsalted butter, melted
2 1/4 cups all purpose flour
1/2 teaspoon baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
2 large eggs
3 egg yolks
1 teaspoon vanilla
12 tablespoons unsalted butter
1 3/4 cup sugar
2 tablespoons molasses
1 tablespoon fresh ginger, grated fine
1 cup buttermilk

Melt the butter in a skillet over medium heat until it gets a light brown color, about 2 to 4 minutes. Once it starts browning, swirl the pan to keep from burning, and keep going until it is golden brown and smells nutty. Add the spices to the butter and stir over the heat for about 15 seconds. Return to bowl and let cool to room temperature, about 30 minutes. Measure the dry ingredients into a bowl and whisk together to mix. Beat the butter, sugar, and molasses at high speed for about 3 minutes. Scrape down the sides of the bowl about halfway through. Beat at medium speed, adding cooled butter/spice mixture. Add the fresh ginger and 1/2 of the eggs. Beat at medium speed for 15 seconds. Add the rest of the eggs and beat 15 seconds. Add 1/3 the dry ingredients and mix about 5 seconds until the flour is blended in. Add half of the buttermilk and mix to combine, then another 1/3 of the flour, mix. Add the rest of the buttermilk, mix, and add the rest of the flour mixture. Dump the batter into a greased and floured glass pan (9 by 13 inch). Run a rubber spatula through the batter in a zigzag to remove air holes, spread the batter to the edges and smooth the top, and tap the pan on the counter to remove more. Bake 30 minutes at 350 until it tests clean. Cool to room temperature on a rack.

Cream Cheese Frosting
5 tablespoons unsalted butter
1 1/4 cup powdered sugar
Reserved 1/2 teaspoon of spice mixture

Beat 2 minutes until fluffy.

8 oz cream cheese, softened and cut into pieces

With mixer on medium speed, add the cream cheese one piece at a time until fluffy and all lumps are gone.

Add 1 teaspoon vanilla

Run a paring knife along the outside of the cake. Frost completely with the cream cheese frosting and sprinkle 3/4 cup coarsely chopped and toasted and cooled walnuts.