01 - Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners or grease thoroughly.
02 - In a large bowl, whisk together flour, poppy seeds, baking powder, baking soda, and salt until well blended.
03 - Rub lemon zest into sugar with fingers until fragrant. Add eggs, yogurt, melted butter, lemon juice, and vanilla extract. Whisk until smooth and fully incorporated.
04 - Pour wet ingredients into dry ingredients. Gently fold with spatula just until combined; avoid overmixing to prevent tough muffins.
05 - Divide batter evenly among muffin cups, filling each approximately 3/4 full.
06 - Bake for 16-18 minutes until toothpick inserted into center comes out clean.
07 - Let muffins cool in pan for 5 minutes, then transfer to wire rack to cool completely before glazing.
08 - Whisk powdered sugar with lemon juice, adding juice gradually to reach desired consistency. Stir in zest if using. Drizzle over cooled muffins and allow glaze to set before serving.