Ingredients

CAKE:

1/2 cup butter, softened

1 cup packed brown sugar

Zest of 1/2 orange

2 large eggs

1 1/3 cups flour

2 tablespoons unsweetened cocoa

2 teaspoons quatre épices

1 teaspoon baking powder

1/2 teaspoon baking soda

1/2 teaspoon salt

1/2 cup buttermilk

FROSTING:

2/3 cup butter

1/4 cup honey

1 teaspoon quatre épices

2 tablespoons half-and-half

1 1/2 tablespoons lemon juice

3 cups powdered sugar

2/3 cup chopped toasted walnuts

Preparation

  1. Preheat oven to 350°. Butter and flour a 9-in. square pan.

  2. Make cake: Beat butter, brown sugar, and zest in a large bowl with a mixer until fluffy. Add eggs and beat until well blended. In another bowl, combine flour and other dry ingredients. Add flour mixture to butter mixture one-third at a time, alternating with buttermilk half at a time, and beating on low speed after each addition until blended. Spread batter in pan.

  3. Bake until a toothpick inserted in center comes out clean, 25 to 30 minutes. Let cool on a rack, 10 minutes. Loosen cake from pan with a slender spatula, then invert onto a rack. Re-invert onto another rack; cool completely.

  4. Make frosting: Cook butter in a medium saucepan over medium-low heat, swirling pan occasionally, until deep golden brown, 10 to 15 minutes. Pour into a mixer bowl, let cool, then chill until firm enough to beat, about 30 minutes. Add remaining ingredients except for nuts and beat until fluffy, 1 to 2 minutes, occasionally scraping inside of bowl.

  5. Split cake horizontally with a long serrated knife. Lift off top layer with 2 wide spatulas. Set bottom layer on a platter, then spread with half of frosting. Replace top layer. Spread top of cake with remaining frosting, then sprinkle with nuts.