In a large bowl, mix together cherries and sweetener. Mash with the back of a fork and then let berries sit 10 minutes.
Mix in cornstarch and extract. Set aside
On a heavily floured surfaced, knead dough a few times and divide into eight balls. Pat each ball into a 4-inch circle. Place each circle in 3½-inch Mason jar lids. Pat down and push dough up the side of the rim of each lid. Prick the bottom of each crust with a fork.
Spoon cherries into each crust.
Place crusts on a baking sheet and bake for about 20 minutes or until the crusts’ edges start to turn golden brown.
Remove from oven and cool slightly. Then remove tarts from each mason jar lid. Serve with a dollop of whipped cream or vanilla yogurt.