Heat oven to 350° F.
Sift the flour, baking powder, baking soda, and a dash of salt into a bowl.
Cream together the butter and sugar until the mixture is light and fluffy.
Beat in the eggs one at a time
Beat in one tablespoon of the lemon zest, the poppy seeds and the vanilla extract. With the mixer on low, beat in about half of the flour. Beat in the sour cream and then beat in the rest of the flour.
Pour batter into a lined muffin pan and bake for about 20 minutes.
If desired, make the glaze by simmering the lemon juice, sugar and zest until the sugar has dissolved. When the muffins come out of the oven, spoon about 1/2 of the glaze over the top. Let it sit over night and spoon the rest of the glaze over the muffins when you take them out of the muffin tin the next day. You can cut back on the glaze if you prefer not to have the outside of the muffins so sweet.