Makes about 6 cups/1.5 L filling
IN THE EARLY 1900s, FARMERS IN THE MIDWEST GREW DOZENS OF VARIETIES OF sour cherries—the tart, smaller, softer cousin to the sweet cherries we love to eat by the bagful when the season hits. These days, 99 percent of the sour cherries grown in the Midwest are of the Montmorency variety, primarily in Michigan and Door County, Wisconsin. Sour cherry season is fleeting and the harvest quite fragile, so when you are lucky enough to come across some, hoarding them is recommended. For what can’t be immediately used, a homemade cherry pie filling is the best way to celebrate your haul.
2¼ pounds/1.2 kg fresh or frozen tart cherries
1 cup/200 g granulated sugar, divided
6 tablespoons/48 g cornstarch
Generous ¼ teaspoon fine sea salt
1 teaspoon freshly squeezed lemon juice (optional)
If using fresh cherries, pit the cherries into a large bowl, discard the pits. Add ½ cup/100 g of the sugar to the bowl and stir to blend. Let sit at room temperature for 1 hour. Drain the cherries, reserving the juice in a small bowl (you should have a little over 1 cup/225 g of juice). Whisk the cornstarch into the juice until dissolved.
If using frozen cherries, thaw them completely, reserving the juice. Drain the cherries, reserving 1 cup plus 2 tablespoons/250 g of the juice in a small bowl (you will have more juice than you need). Lay out the cherries on paper toweling and very gently pat them dry. Whisk the cornstarch into the cherry juice.
In a 3-quart/2.8 L saucepan, combine the cherries, sugar (the remaining ½ cup/100 g if using fresh cherries, 1 cup/200 g if using frozen), cherry juice mixture, and salt. Place the pan over medium-high heat and bring the mixture to a boil. Cook for 2 minutes, stirring gently, until thick and glossy and a clean track remains for 1 to 2 seconds on the bottom of the pot as you stir. Remove the pan from the heat and allow the filling to cool slightly. Taste the filling—if it needs a bit of tartness to really make it sing, add a few drops of lemon juice. Let cool completely before using or ladling into jars. Store in the refrigerator for up to 3 weeks, or in the freezer for up to 1 year.