Preheat oven to 180°C (350°F) and grease a muffin tin or line with cupcake liners.
In a bowl, whisk eggs and sugar until smooth and slightly pale.
Add melted butter, milk, lemon juice, lemon zest, and vanilla extract. Mix well.
Stir in flour and salt until you get a smooth, thin batter.
Pour batter into muffin cups, filling each about ¾ full.
Bake for 25–30 minutes until tops are lightly golden and centers are just set.
Remove from oven and let cool completely in the pan.
Chill for 30 minutes if you prefer a firmer texture.
Serve as is or dust lightly with powdered sugar if desired.