First, preheat the oven to 325 degrees F and line a 12-cup muffin tin with paper liners.
Next, melt the butter in 30 second intervals in the microwave, then set aside and cool for at least 10 minutes.
Then, make your dry mixture. Combine flour, sugar, poppy seeds, baking powder, baking soda, and salt in the bowl of a stand mixer, using the whisk attachment on medium speed.
Next, make your wet mixture. In a separate large bowl, whisk together milk, cream cheese, lemon juice and zest, and vanilla extract until ingredients are well-combined and the cream cheese is fully incorporated. Then, beat in the eggs until thoroughly combined.
Switch to the paddle attachment on your stand mixer. Turn it on to the lowest speed, then slowly pour the wet mixture into the dry mixture to gently fold the ingredients in. Mix until just combined, then turn off the stand mixer and scrape the sides and bottom of the bowl with a rubber spatula. Mix again on low speed until all ingredients are combined well.
Next, pour in the melted butter with the stand mixer set to the lowest speed again. Mix until just combined - avoid overmixing, which can lead to dense muffins.
Finally, divide the batter evenly among the muffin cups, then lightly sprinkle the muffin tops with granulated sugar. Use about a quarter- to a half-teaspoon of sugar per muffin.
Bake on the middle rack of your oven until the muffins are golden and a toothpick inserted in the center of the largest muffin comes out clean, about 20 to 25 minutes.
Cool muffins in the pan for at least 5 minutes, then carefully transfer to a cooling rack. Use a knife to gently separate and loosen under the edges of the muffin tops if they are sticking slightly to the pan. Cool for another 10 minutes before serving, and cool to room temperature before storing.
Notes
Adaptation: This recipe is an adaptation of these Bakery Style Lemon Poppy Seed Muffins by Jessica at A Kitchen Addiction. Read our blog post above to learn what we changed and how the results differ.Lemon zest: If you don't own a zester, use a cheese grater and then mince with a sharp knife to achieve a fine zest. You want to avoid having any large chunks in the batter.Cream cheese: Make sure the cream cheese is completely softened so that it mixes into the batter well. Leave it out at room temperature for about 20 to 30 minutes before baking, and you should be good to go.Storing muffins: Cool the muffins completely before storing in an air-tight container. Store at room temperature for up to 4 days, or freeze in a zip-top bag for up to 3 months.