Combine flour, baking powder, salt, baking soda in a medium bowl and whisk together. Set aside.
In a medium bowl, whisk together sour cream, buttermilk, lemon juice and vanilla. Set aside.
In a large bowl beat sugar, 1 stick of butter and lemon zest. Add eggs and beat until fluffy. Add dry ingredients (from step 2). Add sour cream mixture, and mix until well combined.
Stir in poppy seeds.
Add liners to muffin pan and spoon mixture into each liner. Bake for 20 minutes. Let cool.
For glaze, mix together melted TB of butter, milk and powdered sugar. Add more powdered sugar if it is too runny or more milk if it's too thick. Drizzle over muffins. ENJOY!