1. Preheat oven to 350°F (180°C). Grease a 9×5-inch (or 8×4-inch) loaf pan and line it with parchment paper, leaving an overhang on two sides.

2. In a small bowl, combine the flour, baking powder, baking soda, lemon zest, and salt. Set aside.

3. In the bowl of a stand mixer or using an electric mixer, cream the softened butter and sugar together at medium-high speed until pale and fluffy, about 4 minutes. Scrape down sides as needed.

4. With the mixer running on low, add the eggs one at a time, then beat in the vanilla extract and lemon juice. Beat on medium-high until fully combined.

5. With mixer on low, add one-third of the flour mixture and mix until almost combined, then add half the buttermilk and mix. Repeat, alternating with remaining flour and buttermilk, ending with flour. Beat until just incorporated.

6. Add poppy seeds and fold in with a spatula.

7. Scrape batter into prepared pan and bake for 45–50 minutes, or until a toothpick comes out with a few moist crumbs.

8. Let cake cool 10 minutes in the pan. Stir together lemon juice and powdered sugar for syrup. Transfer cake to a rack and brush syrup over while still warm. Let cool completely.

9. Once cooled, mix icing by combining powdered sugar with lemon juice and just enough milk to make a thick glaze. Spoon over cake and let harden before serving.