Heat the oven to 400 degrees. Line 12 muffin cups with paper liners. Place the milk in a small glass measuring cup. Microwave the milk on high for 45 to 60 seconds or until hot. Stir in the poppy seeds. Let stand for 30 minutes or until room temperature. Whisk the flour, baking powder, baking soda and salt in a small bowl. Beat the sugar, butter and 2 teaspoons lemon zest in large bowl at medium speed for 2 minutes, or until light and creamy. At low speed, beat in 1/2 cup sour cream. Beat in the egg. Slowly beat in the milk and poppy seed mixture. Beat in the flour mixture. Spoon the batter into the muffin cups. Bake for 20 to 25 minutes or until a toothpick inserted in the center comes out clean. Cool in the pan on a wire rack for 10 minutes. Remove from the pan and cool completely. Meanwhile, whisk 3 tablespoons sour cream and 3/4 teaspoon lemon zest in a medium bowl. Slowly whisk in 1 cup of powdered sugar, adding enough additional powdered sugar for desired consistency. Drizzle over the muffins and let stand until set.