Preheat oven to 375°F.
Line a 12-cup muffin tin with liners.
In a large bowl whisk together the dry ingredients: flour, protein powder, poppy seeds, baking powder, baking soda, and salt.
In another bowl whisk together the wet ingredients: eggs, Greek yogurt, melted butter, maple syrup, lemon juice, lemon zest, vanilla, and milk.
Pour wet ingredients into dry and gently fold until just combined. Do not overmix. The batter should be thick but scoopable.
Fill muffin cups almost to the top.
Bake for 18–22 minutes until the tops are lightly golden, centers spring back when touched, toothpick comes out mostly clean *Do not over bake or they will turn out dry!
Cool 10 minutes before glazing.
Drizzle with lemon glaze if desired.