Step 1: Preheat your oven to 350°F (175°C). Lightly grease and flour an 8x4-inch or 9x5-inch loaf pan, or line it with parchment paper leaving an overhang on the sides for easy removal.
Step 2: In a medium bowl, whisk together the all-purpose flour, baking powder, lemon zest, and salt. Set aside.
Step 3: In a large bowl, using an electric mixer, cream together the softened unsalted butter and granulated sugar until light and fluffy, about 4-6 minutes. This step incorporates air, making the cake tender.
Step 4: Add the eggs one at a time, beating well after each addition until fully incorporated. Stir in the vanilla extract and lemon juice, mixing until just combined.
Step 5: With the mixer on low speed, gradually add the dry flour mixture alternately with the buttermilk, beginning and ending with the flour mixture. Mix only until just combined and no streaks of flour remain. Be careful not to overmix.
Step 6: Pour the batter evenly into the prepared loaf pan and smooth the top with a spatula.
Step 7: Bake for 45-55 minutes, or until a wooden skewer or toothpick inserted into the center comes out clean with just a few moist crumbs. Baking times can vary, so keep an eye on it.
Step 8: Let the loaf cool in the pan for about 15-20 minutes before carefully transferring it to a wire rack to cool completely. This prevents it from breaking apart.
Step 9: While the cake cools, prepare the lemon glaze. In a small bowl, whisk together the confectioners’ sugar, fresh lemon juice, and optional milk until smooth and pourable. Adjust consistency by adding more sugar for a thicker glaze or more lemon juice/milk for a thinner one.
Step 10: Once the loaf is completely cool, drizzle the lemon glaze generously over the top, allowing it to drip down the sides. Let the glaze set for a few minutes before slicing and serving.