In a bowl, mix flour, poppy seeds, baking soda, and salt.
In another bowl, beat butter and sugar until well blended. Add eggs and beat until incorporated. Beat in lemon peel and lemon juice. Add half the flour mixture and stir just until evenly moistened, then stir in milk and remaining flour mixture. Spoon batter equally into 12 paper-lined muffin cups.
Bake in a 350° regular or convection oven until tops are browned and a wooden skewer inserted in the center comes out clean, 15 to 18 minutes. Let stand on a rack 5 minutes, then remove muffins and let cool completely.
Dip top of each muffin in lemon glaze; allow excess to drip off. Return to rack until glaze is set, about 15 minutes.
Lemon glaze: In a bowl, mix 1/2 cup powdered sugar, 2 tablespoons lemon juice, and 1/2 teaspoon vanilla until smooth. Use immediately.
Nutritional analysis per muffin.