Preheat the oven to 325°F. Line a standard muffin tin with paper liners.
In a large bowl whisk together the flour, sugar, poppy seeds, baking powder, baking soda, and salt.
In a small bowl whisk together the milk, butter, egg, juice, and zest. Pour into the dry ingredients and stir with a rubber spatula until just combined. Do not overmix, there should be a couple streaks of flour remaining. Divide evenly among the muffin tin cups.
If time permits, cover and refrigerate the batter overnight for taller more tender muffins.
Bake until golden brown and a toothpick inserted in the center comes out clean and the edges are golden, about 18-20 minutes. Let cool until barely warm.
Glaze:
In a small bowl, combine the powdered sugar and lemon juice until smooth. Drizzle over top of muffins. Let set before serving.