Preheat the oven to 350°F.
Combine the flax meal and water in a small bowl and set aside for 10-15 minutes.
Combine the milk and lemon juice and set aside for 10-15 minutes.
In a medium mixing bowl, combine the flour, baking powder, baking soda, salt and poppy seeds.
In a separate large mixing bowl, whisk the melted butter or oil with the sugar. Add in the milk + lemon juice mixture, sour cream, lemon zest, vanilla and flax egg and mix until comined.
Fold the dry ingredients into the wet until just combined.
Pour into a greased muffin pan. Bake for 18-20 minutes or until a toothpick inserted in the center comes out clean or with a few crumbs.