Preheat the oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or grease the cups lightly.
In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, poppy seeds, baking powder, and salt until well combined.
In a separate medium bowl, whisk together the whole milk, vegetable oil, eggs, vanilla extract, lemon zest, and fresh lemon juice until smooth.
Pour the wet ingredients into the dry ingredients and gently stir with a spatula or wooden spoon until just combined. Do not overmix; the batter should be slightly lumpy.
Divide the batter evenly among the 12 muffin cups, filling each about 3/4 full.
Bake in the preheated oven for 18 to 20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Remove the muffins from the oven and allow them to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely before serving.