Line a 9x5 loaf pan with parchment paper. I don't worry about covering both ends, just the center and the sides. Spray the ends of the pan and the bottom of the parchment paper with a light spray of nonstick spray.
In a stand mixer with the paddle attachment (or in a large bowl with a hand mixer), cream butter and sugar together on medium speed until light and fluffy, about 2-3 minutes.
1 cup salted butter, 1½ cups granulated sugar
Beat in eggs one at a time.
3 eggs
Add orange zest and vanilla and stir well.
2 tablespoons orange zest, 1 teaspoon vanilla
Combine flour, baking soda and salt. Add half of the flour mixture to the batter and combine.
3 cups flour, ½ teaspoon baking soda, ½ teaspoon salt
Mix in buttermilk.
1 cup buttermilk
Add remaining flour and stir just until blended.
Place batter in prepared loaf pan and smooth batter with a spatula.
Bake in preheated oven for 70-80 minutes or until fully cooked through. Test with a toothpick to determine when cake is cooked through.
Cool cake in pan for 10 minutes, then remove cake from pan on a baking rack for another 10 minutes, then brush top and sides of cake with orange glaze. Brush each side 2-3 times.
Orange Glaze
While the cake is baking, combine sugar and orange juice. The sugar will slowly dissolve over time. Stir the mixture 1-2 times while cake is baking.
2 tablespoons granulated sugar, 2 tablespoons orange juice
Orange Icing
Once the cake is fully cool, mix the icing. Combine powdered sugar and orange juice in a bowl. Whisk until smooth.
1 cup powdered sugar, 2 tablespoons orange juice
Drizzle orange icing over the top of the cake. Allow icing to harden, then slice and serve. The icing may take 30-60 minutes to fully harden.
Notes
Make certain your butter is softened to room temperature.
If using unsalted butter, add an additional ¼ teaspoon of salt to the flour mixture.
The cake can be baked without parchment paper, just grease and flour your pan before baking. Shake off any excess flour.
Use a toothpick inserted in the center of the cake to determine if the cake is baked through. This cake has a large amount of batter and it takes a while for it to bake through. If the top is becoming too dark, tent lightly with foil.
The orange glaze adds extra flavor and moisture to the cake. You will probably not use all the glaze.
This cake is best eaten the same day it is made. If making ahead of time, allow the cake to fully cool and then place in an airtight container. Then next day, add the glaze to the cool cake and then add the icing.