Center rack in oven and preheat to 400°F
Oil 12-spot regular-sized muffin pan or fit with paper cups.
In the bowl of a stand mixer, mix the sugar and lemon zest together with your fingers. Whisk in the flour, baking powder, baking soda, and salt.
In a small bowl mix together the sour cream, eggs, vanilla, lemon juice, and melted butter.
Pour the liquid ingredients over the dry and mix on low to blend. Stir in the poppy seeds.
Divide the batter evenly among the muffin cups. Only fill them ~¾ full as they'll rise a bit during baking.
Bake for 18-20 minutes or until tops are golden brown and a toothpick inserted in the middle comes out clean. (see notes)
Transfer pan to a rack and let cool for five minutes before removing each muffin. Cool muffins completely before glazing.