Adjust oven rack to middle position and preheat oven to 425ºF (220ºC). Using nonstick spray, lightly grease two 12-cup muffin tins (or 12 individual tart tins); set aside.

On a generously floured work surface, use a rolling pin to roll pie crust dough into a 12- by 16-inch rectangle about ¼-inch thick. Using a round 4-inch cookie cutter or jar, cut 18 circles out of the dough, rerolling the dough as needed, about 3 times. (If dough is too soft or sticky to work with, refrigerate briefly before continuing to roll.)

Working with one circle of dough at a time, press dough into the well of muffin tin, starting from the center to edges, until dough reaches the edge of the well. Repeat with remaining dough. Transfer muffin tin to fridge and chill until firm, about 30 minutes. (Alternately, use the same method to press the dough into 12 individual tart tins.)

Meanwhile, prepare the filling: In a medium bowl, whisk melted butter and brown sugar together. Add eggs, vanilla extract, salt, and vinegar and whisk until smooth. (The filling will be fairly runny.)

Fill tart shells with 1 ½ tablespoons of filling; do not overfill. Bake for 10 minutes, then reduce oven temperature to 350ºF (175ºC). Continue baking until filling is bubbly, deeper in color, and pastry is golden, about 12 minutes. Remove from oven and allow tarts to cool in pan for 10 minutes; use a butter knife to gently separate tarts from the tin, then transfer to a wire rack to cool completely, about 1 hour.