Prepare the Crumb Crust and Topping:

1. Preheat the oven to 375ºF and place oven racks in the lowest and middle parts of the oven. Butter or oil an 8-inch square (or similar size) baking dish. Cut a strip of parchment to fit inside the dish with ends long enough to hang over the edges. Line the baking dish with the parchment and set aside.
2. In a medium bowl, whisk together the melted butter, granulated sugar, baking powder, vanilla, and salt. Stir in the flour until just combined.
3. Sprinkle ⅔ of the crumb mixture into the prepared baking dish as evenly as possible. Using a flat-bottomed measuring cup or your hands, press the mixture into an even layer. Bake the crust on the lowest rack until it's lightly golden on the edges with a matte appearance in the middle, about 12 minutes. Remove and set aside until ready to use.

Make the Cherry Pie Filling:

1. Meanwhile, in a medium pot, stir together the granulated sugar, tapioca starch, and salt. Add the cherries, lemon juice, and almond extract and cook over medium heat, stirring frequently, until the mixture is bubbling throughout, about 5 minutes. Remove from the heat and let cool for at least 10 minutes.
2. Transfer the cherry pie filling onto the par-baked crust and spread into an even layer. Sprinkle the remaining crumb mixture evenly on top.
3. Bake on the middle rack until the filling is slightly puffed and the crumb mixture is light golden, 30 to 35 minutes.
4. Transfer to a wire rack and let cool completely.
5. Cut into 16 pieces and serve. Store at room temperature in a covered container for up to 1 day, or in the refrigerator for up to 2 to 3 days.