Preheat oven to 450 degrees F (230 degrees C). Spray twelve 3-inch tart tins with cooking spray.
Roll out pie crust on a lightly floured surface and cut twelve 4-inch circles with a cookie cutter, rerolling scraps if necessary. Line tart tins with pastry circles.
Beat eggs, brown sugar, vinegar, and vanilla together in a bowl until smooth; stir in melted butter, cherries, and walnuts. Fill tart shells 2/3 full with butter mixture.
Bake in the preheated oven for 10 minutes. Reduce oven temperature to 350 degrees F (180 degrees C) and continue baking until crust is golden and filling is bubbling, about 20 minutes.
Remove tarts from oven; sprinkle evenly with toffee bits. Return tarts to the oven; bake until toffee bits are just melted, about 5 minutes. Cool on a wire rack, about 15 minutes. Gently lift tarts from tins.