1) Preheat oven to 350 degrees. Line muffin tins with paper liners.
2) Whisk flour, baking powder, salt, and baking soda in medium bowl.
3) Whisk sour cream, buttermilk, and lemon juice in small bowl to blend.
4) Using electric mixer, beat sugar, butter, and lemon zest in large bowl to blend.
5) Add eggs one at a time, beating well after each addition until mixture is light and fluffy, occasionally scraping down sides of bowl.
6) Beat in dry ingregientsin 3 additions alternately with sour cream/buttermilk mixture in 2 additions. Mix just until blended.
7) Stir in poppy seeds. Spoon batter into prepared muffin cups.
8) Bake muffins until tester inserted into center comes out clean, 20-22 minutes. Cool in pans 5 minutes.
9) Remove muffins from pans and cool on rack.
10) Mix together melted butter, lemon juice, and enough powdered sugar to make a glaze. Drizzle or pipe glaze over tops of warm muffins.
11) Makes 48 mini muffins or 12 large muffins.