01 - Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners or lightly grease with butter.
02 - Whisk together flour, sugar, poppy seeds, baking powder, baking soda, and salt in a large bowl until thoroughly combined.
03 - Whisk eggs, Greek yogurt, melted butter, lemon zest, lemon juice, and vanilla extract in a separate bowl until smooth and creamy.
04 - Gently fold wet ingredients into dry ingredients using a spatula. Mix until just combined, taking care not to overmix as this can result in dense muffins.
05 - Divide batter evenly among prepared muffin cups, filling each approximately three-quarters full.
06 - Bake for 16 to 18 minutes, or until a toothpick inserted into the center comes out clean and tops are golden brown.
07 - Allow muffins to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely before glazing.
08 - Whisk powdered sugar and lemon juice until smooth and pourable. Add additional lemon juice if needed to achieve desired consistency.
09 - Drizzle glaze over completely cooled muffins. Sprinkle with additional lemon zest if desired. Serve immediately or store as directed.