For the cake:
3 cups cake flour
1 teaspoon salt
1/2 teaspoon baking powder
1/2 teaspoon baking soda
3/4 cups buttermilk
1/4 cup lemon juice
16 tablespoons (8 ounces) unsalted butter, softened to room temperature
2 1/2 cups sugar
Zest from 2 lemons
5 large eggs
2 teaspoons vanilla extract
For the glaze:
3/4 cup powdered sugar
1 tablespoon buttermilk
1 tablespoon lemon juice
Preheat the oven to 350°F. Place an oven rack in the bottom third of the oven. Line two 8×4-inch loaf pans with parchment and spray with cooking spray.
Sift together the flour, salt, baking powder, and baking soda in a small bowl.
Whisk together the buttermilk and lemon juice in a measuring cup.
Beat the butter, sugar, and lemon zest: Start on low speed and gradually increase to medium-high once the butter and sugar are incorporated. Continue beating until the mixture becomes light and fluffy, and starts to clump together.
Add the eggs and vanilla: Mixing on medium speed, beat in the eggs one at a time. Make sure each egg is fully incorporated before adding the next one, and scrape down the sides of the bowl as needed. After adding all the eggs, add the vanilla. Scrape down the bowl.
Add the flour mixture and buttermilk mixture: Add a fourth of the flour mixture and beat on low speed until just barely incorporated. Add a third of the buttermilk mixture, and again, beat until just barely incorporated. Continue alternating between adding the flour and the buttermilk, beating slowly between each addition and ending with the last of the flour.
Scrape down the bowl: Use a rubber spatula to gently scrape down the sides and bottom of the bowl to incorporate any last bits of flour and any lumps.
Divide between loaf pans: Divide the batter evenly between the loaf pans and smooth the tops.
Bake for 50 to 60 minutes: Rotate the pans once during baking. Bake until the cakes are deep golden on top with a crease down the middle and a cake tester inserted in the middle comes out clean.
Cool for 10 minutes in the pan.
Cool completely: Lift the cakes from the pans using the parchment paper and transfer to a cooling rack. Cool completely.
Glaze the loaves: About an hour before serving, whisk together the ingredients for the glaze — it should be thick but pourable. Add a little more liquid or a little more sugar if needed to thin or thicken. Spoon the glaze over the cakes and allow to set.