Preheat your oven to 350°F (175°C). Grease a muffin tin or line it with paper liners for easy removal.
In a large mixing bowl, whisk together the sweetened condensed milk, lemon juice, and eggs until smooth. Stir in the melted butter, self-rising flour, vanilla extract, and lemon zest. Mix until well combined and no lumps remain.
Divide the batter evenly among the prepared muffin cups, filling each about ¾ full.
Bake in the preheated oven for 18–22 minutes, or until the pies are golden brown on top and set in the center. Test for doneness: A toothpick inserted into the center should come out clean.
Let the pies cool in the muffin tin for 5–10 minutes, then carefully transfer them to a wire rack to cool completely. Serve plain or dust with powdered sugar for an elegant touch.
