01 - Preheat oven to 350°F. Grease a 9x5-inch loaf pan and line with parchment paper.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, salt, and poppy seeds until well combined.
03 - In a large bowl, whisk sugar and eggs until thick and pale, about 2 minutes. Add milk, melted butter, lemon juice, lemon zest, and vanilla extract; whisk until smooth.
04 - Gently fold the dry ingredients into the wet mixture until just combined. Do not overmix—a few small lumps are acceptable.
05 - Pour batter into the prepared loaf pan and smooth the top. Bake for 45-55 minutes, or until a toothpick inserted into the center comes out clean.
06 - Let the loaf cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before glazing.
07 - In a small bowl, whisk together powdered sugar and enough lemon juice to make a thick, pourable glaze.
08 - Drizzle the glaze over the cooled loaf. Allow it to set for 15-20 minutes before slicing.