In a large mixing bowl, fit with the whisk attachment, beat the butter and sugar until light and fluffy. Add one egg at a time, scraping sides of bowl if necessary. Add the lemon zest, 2 1/2 tbsp lemon juice, and vanilla extract, continue to beat until smooth.
In a separate bowl whisk together the flour, baking powder, baking soda and salt.
Alternately add 1 cup of the flour mixture, greek yogurt, and sour cream to the wet ingredients, until all the flour is used. Don't over mix. Add the poppy seeds and stir to evenly incorporate.
Divide the batter evenly among the lined muffin cups.
Bake for 20-25 minutes or until muffins are lightly golden brown on top. Remove from oven and let cool on wire rack.
To make Lemon Glaze
Combine the powdered sugar and lemon juice in a small bowl, whisk until smooth. Add more lemon juice if you would like the glaze thinner. Brush on top of each muffin, and let harden.