Pull the stem off the cherry and place it, stem-side down, in a bottle with a narrow neck, like a beer bottle. Drive the blunt end of a chopstick down through the cherry, forcing the pit out into the bottle.
Mix together the pitted cherries, sugar, and cornstarch in a bowl and let it sit for ten minutes or so until they get juicy.
Stir the almond extract into the cherry mixture and heat in a heavy pot over medium heat. Bring to a boil. Lower heat and simmer over medium heat, stirring constantly, for several minutes. Stir in the butter.
Let the mixture cool a bit, then pour into pie shells.
This would also be fine over ice cream.