Preheat the oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners.
In a mixing bowl, whisk together flour, sugar, baking powder, salt, and poppy seeds.
In another bowl, whisk melted butter, eggs, milk, lemon juice, lemon zest, and vanilla extract.
Combine wet and dry ingredients until just combined. Divide batter evenly into liners using a scoop or spoon.
Bake for 18–20 minutes or until a toothpick comes out clean. Cool in the tin for 5 minutes, then transfer to a wire rack.
Whisk powdered sugar, lemon juice, and zest to make glaze. Drizzle over cooled cupcakes.
