1. Preheat your oven to 375°F (190°C) and line a muffin tin with paper liners or grease the cups.
2. In a large mixing bowl, whisk together the brown sugar and melted butter until smooth.
3. Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next.
4. Add the yogurt, vanilla extract, and lemon juice to the wet ingredients, and stir to combine.
5. In a separate bowl, mix the flour, baking powder, salt, and poppy seeds.
6. Gradually add the dry ingredients to the wet ingredients, alternating with the milk, and stir just until combined.
7. Gently fold in the lemon zest.
8. Divide the muffin batter evenly among the muffin cups, filling each about 2/3 full.
9. Bake for 18-22 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
10. Let the muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.

For the Lemon Sugar Glaze (Optional):

1. In a small bowl, mix the powdered sugar, lemon juice, and lemon zest until smooth.
2. Drizzle the glaze over the cooled muffins for an added touch of sweetness and citrus flavor.