Preheat the oven to 350°F (175°C). Lightly grease a 12-cup muffin tin or mini pie pans.
In a large bowl, whisk together the flour, sugar, baking powder, and salt.
In a separate bowl, beat the eggs, then add the milk, lemon juice, lemon zest, and vanilla extract. Mix well.
Gradually add the wet ingredients to the dry ingredients, stirring gently until combined. Do not overmix. The batter will be thin.
Pour the batter evenly into the prepared muffin cups, filling about 3/4 full.
Bake for 25-30 minutes or until the tops are golden and a toothpick inserted in the center comes out clean.
Remove from oven and let cool slightly before removing from the pans.
Dust with powdered sugar before serving. These little pies have a light, custard-like texture with a refreshing lemon flavor.