Instructions
Step 1
Make the crumb: In a large bowl, mix the flour, both sugars, the cinnamon, and salt. Add the butter and squeeze the mixture firmly and repeatedly with your fingers, scooping up the bits from the bottom of the bowl until the mixture feels moist and comes together in golf-ball-size crumbles. Cover the bowl with plastic wrap and refrigerate until firm, about 30 minutes.
Step 2
When ready to bake, set a rack in the center of the oven and preheat to 350°F. Gently pit the cherries, recruiting help as needed, and transfer to a large bowl. Stir in the tapioca flour, sugar, vanilla, zest, cinnamon, and salt.
Step 3
Quickly transfer the cherry mixture to a 10-inch ceramic baking dish or pie plate. Sprinkle the topping evenly on top to cover the cherries, crumbling it into smaller pieces as you go.
Step 4
Bake on a foil-lined, rimmed baking sheet until the juices are thickened, syrupy, and bubbling slowly and the top is lightly golden, about 50 minutes. Remove to a wire rack and let cool completely (or nearly). Serve with vanilla ice cream.