Step 1: Preheat your oven to 350°F (175°C) and line your muffin tin with parchment paper liners.
Step 2: In a large mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, and sea salt until well combined.
Step 3: In another bowl, beat together the Greek yogurt, eggs, granulated sugar, melted butter, milk, lemon juice, lemon zest, and vanilla extract.
Step 4: Pour the wet ingredients into the bowl of dry ingredients. Gently fold them together until just combined.
Step 5: Sprinkle in the poppy seeds and gently fold them into the batter.
Step 6: Divide the batter evenly among the prepared muffin cups, filling each about 2/3 full.
Step 7: Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Step 8: Let cool in the tin for 5 minutes before transferring to a cooling rack. Drizzle with lemon glaze if desired.