Position one rack in the middle of the oven, and preheat the oven to 350 degrees F. Grease 12 muffin cups or line 12 muffin?cups with muffin papers.
In a stand mixer with the whisk attachment or with a handheld mixer, cream the butter and sugar until light and fluffy,?about 3 minutes. Gradually add the eggs, and mix until fully combined. In a small bowl, combine the poppy seeds, lemon zest, the lemon juice, and the vanilla extract. Add to the butter?mixture and mix until well combined.
In a separate bowl, add the flour, baking soda, baking powder, and salt and whisk together. Add half of the dry?ingredients to the butter mixture and mix slowly until almost combined. Add the sour cream, and mix until almost?combined. Finally add the remaining dry ingredients and mix just until barely moistened. Be very careful not to?overmix this batter.?Gently scoop the batter into the prepared muffin cups.
Bake in a preheated oven for 16 minutes, rotating the pan?from front to back halfway through the baking time. Bake for 3 to 5 more minutes, or until a toothpick inserted in the?center of a muffin comes out clean. Watch the muffins carefully and do not overbake!? While the muffins are baking, in a small bowl, combine the lemon juice and sugar to make a glaze. Just as the?muffins are removed from the oven, brush the lemon glaze generously over each one to moisten.
Allow the muffins?to cool in the pan for 10 minutes, then remove them from the pan and place on a wire rack to finish cooling. Serve?these muffins warm from the oven or within 8 hours after baking. Wrap the remaining muffins in plastic film to keep?them moist