Preheat the oven to 325°F. Lightly butter a 9-inch nonstick baking pan. Place a baking sheet on the lowest oven rack.

In the top of a double boiler, melt the chocolate over just-simmering water. It should be warm, but not hot. Allow it to cool slightly at room temperature.

In the bowl of an electric mixer, cream together the butter and sugar, using the paddle attachment at medium speed (or use a hand-held mixer). Add the eggs one at a time, making sure each is incorporated before adding the next. In 2 separate bowls, combine the flour and baking soda, and the buttermilk and vanilla. Add the 2 mixtures to the creamed mixture alternately. Add the melted chocolate, pecans, and zest and blend thoroughly.

Pour the batter into the prepared pan, place it on the rack above the baking sheet, and bake until the cake is light golden brown and a toothpick inserted comes out dry, about 40 minutes. Cool it in the pan for 5 minutes; then invert onto a cake rack to finish cooling.

For the orange crème anglaise:

In a small bowl, whisk together the egg yolks and sugar, and set aside.

In a small saucepan over high heat, reduce the juice and zest until thick, bubbly, and syrupy, about 10 to 12 minutes.

Meanwhile, in a small, heavy saucepan, scald the cream and milk with the vanilla been over high heat. Add them to the reduced juice and stir to combine. Whisk a little of the cream-juice mixture into the reserved egg mixture and then pour back into the pan of cream. Cook over low heat, stirring with a wooden spoon until the mixture coats the back of the spoon, about 1 minute. Do not allow the mixture to boil. Strain through a fine sieve into a bowl set into a larger bowl of ice cubes and cool completely; then refrigerate.

To serve:

Sprinkle confectioners’ sugar over the top of the cake, if desired, and slice. Spoon about 2 tablespoons of crème anglaise over each slice of cake.

Variations:

Instead of crème anglaise, serve with:

Ice cream

Fresh fruit

Serve orange crème anglaise with Simple Chocolate Cake.

For pecans, substitute almonds.