Preheat oven to 400°F. In a large bowl, combine 2 ½ cups all-purpose flour, 2 teaspoons baking powder, 1 teaspoon baking soda, and s½ teaspoon saltalt, then set aside.
In a separate bowl, whisk together the melted ½ cup unsalted butter, ¾ cup granulated sugar, and ½ cup brown sugar.
Whisk in 2 large eggs, 1 cup whole milk, and 2 teaspoons vanilla extract until well combined.
Fold in the dry ingredients, mixing until just combined.
Fold in 3 tablespoons lemon zest and 2 tablespoons poppy seeds.
Line a 12-count muffin tin with muffin liners or grease heavily. Fill each muffin cup until it is almost full.
Bake in the preheated oven for 5 minutes, then turn the temperature down to 350°F. Bake for 14-17 more minutes until the centers are completely set, verified with a toothpick inserted in the center.
Allow the muffins to cool, then serve!