Preheat oven to 410º F (210° C). Place muffin liners in a 12 large muffin tin. In a medium bowl, sift the flour with the baking powder, baking soda and salt.
Separately, in a large bowl, add in the sugar with the lemon zest and using your fingertips, rub them together. This will help bring out the oils from the lemon zest, giving the muffins more flavor.
Add in the eggs, melted butter, sour cream, milk, lemon juice and vanilla extract. Beat with a hand whisk or an electric mixer for 2 minutes until you get a lighter, fluffier mixture.
Add the flour mixture in two separate additions, beating for 10 seconds after each one to get a smooth batter. Finally, add the poppy seeds and beat just until incorporated.
Carefully pour the batter into the 12 muffin cups, filling each one 3/4 full. Bake the muffins at 410º F (210° C) for approximately 18-20 minutes or until lightly golden brown on top or when a wooden toothpick comes out clean when inserted.
While the muffins are baking, to make the glaze add to a medium bowl the powdered sugar with the lemon juice and mix with a fork for a few seconds until a slightly thick glaze is formed.
Take the muffins out of the oven, let them cool down for at least 15 minutes and then decorate them with the glaze.