This is the recipe that we use for the Door County sour cherries that we pick each year. We tend to make this recipe more often as a topping for waffles or pancakes than as a pie filling.
1 cup sugar
3 tablespoons corn starch
4 cups cherries with their juice
1 tablespoon butter (optional)
1/2 teaspoon almond extract
Mix sugar and cornstarch in a 4-quart sauce pan. Add cherries and mix.
Heat on medium heat until boiling. Cook for 1 minute more.
Remove from heat. Add butter and almond extract. Let cool.
Put filling in a pie shell. Top with another crust. Vent the crust by cutting slices in it. Alternatively, use a lattice crust for the top.
Bake 25-30 minutes at 425°. The crust will be golden brown and the cherry filling should start to bubble on the edges when the pie is done.