Preheat the oven to 350°F. Generously butter a 9 x 5 inch loaf pan, then add a bit of flour and shift the pan around so that the insides are all well coated.
Combine the flour, baking powder, baking soda, and salt in a medium bowl. In another small bowl combine the buttermilk and 1/3 cup lemon juice.
Place the butter and granulated sugar in a mixing bowl and blend until well combined and fluffy, about 3 minutes. Beat in the eggs one at a time, then beat in the lemon zest and vanilla.
Add one third of the flour mixture to the butter mixture and blend just until combined, then add half of the buttermilk mixture, beat until combined, then a third of the flour, beat, the rest of the buttermilk mixture, beat, and finally the last third of the flour mixture, and beat until well blended.
Transfer the batter to the prepared pan. Bake for about 50 to 60 minutes, until you can insert a wooden skewer in the middle of the loaf and it comes out clean. Cool the cake in the pan on a wire rack for 10 minutes, then turn the cake out of the pan and continue cooling it completely on the wire rack, top side up.
When the cake is cool, or almost cool, make the Glaze. Place the confectioners’ sugar and 2 tablespoons lemon juice in a small bowl and stir until smooth. Pour the glaze over the cooled cake, allowing some to drip down the sides.
Notes
You can double this recipe and bake two lemon loaf cakes, and give one to a pal, which is always a wonderful thing to do.