Preheat your oven to 350°F (175°C). Grease a mini muffin tin or mini pie pans with butter or non-stick cooking spray.
In a mixing bowl, combine the sweetened condensed milk, lemon juice, eggs, melted butter, self-rising flour, vanilla extract, and lemon zest. Use a whisk or electric mixer to mix until the ingredients are well combined and smooth.
Pour the mixture evenly into the prepared mini muffin tin or pie pans, filling each cup about three-quarters full.
Bake the pies in the preheated oven for 20-25 minutes, or until they are set and a toothpick inserted into the center comes out clean.
Once the pies are done baking, remove them from the oven and let them cool in the pan for about 5 minutes. Then, transfer the pies to a cooling rack to cool completely. Dust the pies with powdered sugar.
Serve the Baby Lemon Impossible Pies at room temperature for the best flavor and texture.