2 1/4 cups all-purpose flour
2 1/14 teaspoons baking powder
3/4 teaspoon baking soda
1 teaspoon kosher salt
3/4 cup sour cream
1 tablespoon cointreau (optional)
1 1/2 teaspoons vanilla extract
1/4 cup fresh orange juice
1 cup granulated sugar
3 tablespoons orange zest (from about 3 oranges)
3/4 cup (6 ounces) unsalted butter, softened
3 large eggs
1 1/2 cup confectioners’ sugar
2 tablespoons fresh orange juice
Preheat the oven to 350°F. Butter a 9-by-5-inch loaf pan, line the 2 long sides and bottom with one piece of parchment, and dust with flour.
Whisk together the flour, baking powder, baking soda, and salt in a medium bowl. Combine the sour cream, vanilla, Cointreau (if using), and orange juice in a large measuring cup. Set both aside.
In the bowl of an electric mixer fit with the paddle attachment, combine the sugar and orange zest on low speed until fragrant. Drop in the butter 2 tablespoons at a time until it is all added. Increase the speed to medium-high and cream the mixture until it is light and fluffy, about 5 minutes. On low speed, add the eggs, one at a time, beating well after each addition. Scrape the sides and bottom of bowl as you go. Alternately add the flour and sour cream mixtures, beginning and ending with the flour, and mixing only until just combined. Scrape the batter into the prepared pan and smooth the top with a spatula.
Bake the loaf for 45 to 60 minutes, or until a cake tester emerges clean. Let the cake cool for about 10 minutes before releasing it from the pan. To prepare the glaze, combine the confectioners’ sugar and orange juice in a small pan and bring to a boil, stirring once or twice. Simmer for 2 minutes, then remove from the heat and brush/pour over the warm cake. Let the cake cool completely before serving. Use a serrated knife to slice cake, as the glaze will be hard.