These muffins are quick and easy to make, so I highly suggest pulling all your ingredients, measuring cups, and measuring spoons out before you begin.Place your muffin liners in the muffin tin and set aside.Next, preheat your oven to 400F.In a bowl, whisk together the flour, sugar, poppy seeds, baking powder, baking soda, and salt. Set aside. In another bowl, mix together the milk, sour cream, melted butter, egg, lemon zest, and vanilla. Combine the flour mixture with the liquid mixture and hand mix until combined. With your scoop, fill each muffin liner about 3/4 full. Bake at 400F for 5 minutes, then turn the temperature to 350F and bake for 11-13 more minutes. Do not open the door when turning the temperature down. Once the muffins are golden and you can insert a toothpick in the center and it comes out clean, you'll remove them from the oven and let them cool. Let them cool in the muffin tin for about 5 minutes, then place them on a wire rack to finish cooling. Once the lemon poppy seed muffins have cooled, it is time to glaze them. In a small bowl, combine the melted butter, salt, lemon zest, lemon juice, and powdered sugar. Whisk the mixture until it is well combined. Drizzle the glaze over the lemon poppy-seed muffins. Enjoy!The lemon poppy seed muffins will keep at room temperature for 3-5 days in an air-tight container or in the fridge in an air-tight container for 5-7 days.