01 -
Set your oven to 350 degrees. Line a 9-inch square pan with parchment paper or give it a light greasing.
02 -
Put the cherries, brown sugar, lemon juice, and vanilla in a medium saucepan. Cook over medium heat for 3 to 4 minutes, stirring often, until the cherries start releasing their juice.
03 -
Stir in the tapioca starch and keep cooking for another 2 to 3 minutes until it thickens up. Take it off the heat and let it cool a bit.
04 -
Add the flour, oats, brown sugar, baking powder, and salt to a food processor. Pulse a few times to mix everything together.
05 -
Toss in the cold butter cubes and pulse until it looks like coarse crumbs with small pea-sized pieces. Beat the egg lightly in a small bowl, then add it to the processor and pulse just until it starts coming together. It should still look crumbly but hold together when you press it.
06 -
Scoop out about 1 heaping cup of the mixture and set it aside for topping the bars later.
07 -
Press the rest of the mixture firmly and evenly into the bottom of your prepared pan.
08 -
Spread the cherry filling evenly over the crust. Sprinkle the reserved oat mixture on top of the cherries.
09 -
Bake for 40 to 45 minutes until the top turns lightly golden and you see the filling bubbling around the edges. Let it cool completely in the pan on a wire rack.
10 -
Whisk the lemon juice into the powdered sugar first, then gradually whisk in the milk until you get a thick but pourable glaze. Add more milk a few drops at a time if needed. Drizzle over the cooled bars.