Preheat oven to 375º F. Spray muffin tins with bakers spray or coat well with shortening or butter and flour, making sure to discard any excess flour from the tins after coating.
Sift together flour, baking powder, and salt in a medium bowl. Set aside. Pour milk into measuring cup and add lemon juice. Allow to sit while preparing other ingredients.
Cream together butter and sugar until lightened in color, about 3 minutes. Add an egg, one at a time, taking care to fully incorporate before adding the other. Mix in vanilla, lemon zest, and poppy seeds.
Gently fold in flour mixture, alternating with milk. Stir until just combined. Scoop mixture into prepared muffin tins, filling about 2/3 to 3/4 full. Bake until a toothpick or skewer inserted in the middle comes out clean, about 30 minutes.
Prepare glaze topping for muffins while the muffins are baking by stirring together until well-combined.
Once muffins have baked, remove from the oven and allow to cool slightly in the muffin tin. Then, remove each muffin and drizzle with lemon glaze. Place onto a plate to finish cooling or serve slightly warm.