For the filling:
6 to 7 cups fruit, enough to almost fill pan
1/2 to 1 cup sugar, depending on the sweetness of the fruit
1 to 3 teaspoons lemon juice, to taste
1 to 3 tablespoons cornstarch, depending on juiciness of fruit
1 teaspoon spice, like cinnamon, ginger, or nutmeg (optional)

For the crumble topping:
1 cup (5 ounces) all-purpose flour
1/2 cup (4 ounces) brown sugar
1 teaspoon baking powder
1/2 teaspoon cinnamon (optional)
1/4 teaspoon salt
8 tablespoons (4 ounces) unsalted butter, softened

Equipment
9x9-inch or 11x7-inch glass baking dish
Pastry brush
Mixing bowls
Gallon-size zip-top freezer bag (optional)
Whisk
Cooling rack
Instructions