Preheat oven to 350°F (177°C). Line a 9-inch square baking pan (I love this one and this one) with parchment paper, leaving an overhang on the sides to easily lift the bars out of the pan. Set aside.

Whisk the flour, 1 cup (85g) oats, brown sugar, baking powder, lemon zest, and salt together in a medium bowl. Add the melted butter and vanilla, and stir until the mixture resembles moist crumbly sand and no dry spots remain. You will have a little more than 3 cups of crust mixture, or about 520g. Press 2/3 of the mixture (about 2 cups/345g—doesn’t have to be exact) into the prepared baking pan. Press it into the pan (with your hands, a large spoon or spatula, or the bottom of a measuring cup) to form a crust. Bake for 10 minutes, and then remove from the oven to slightly cool.

Place the cornstarch in a small bowl and set aside, within reach of the stove. In a medium saucepan set over medium heat, combine the cherries, sugar, and lemon juice. Cook, stirring occasionally, until the cherries begin to release their juices—about 4 to 6 minutes. While the cherries continue to cook, carefully remove a couple of spoonfuls of the juice from the saucepan and add to the bowl of cornstarch. Using a fork, mix the cornstarch and cherry juice together until the cornstarch is dissolved. Stir this mixture into the filling, then bring to a boil and cook, stirring occasionally, until the filling has thickened, about 10 minutes. Remove from heat and stir in the almond extract.

Pour/spread the filling over the warm crust. Stir 2 Tablespoons oats into the remaining crumble mixture, then sprinkle it all over the filling, and lightly press it down with the back of a large spoon or flat spatula.

Bake for about 40–50 minutes or until the top is lightly browned and a toothpick comes out *mostly* clean (with a few jammy cherry specks!). Mine take about 45 minutes.

Remove from the oven and allow the bars to cool completely in the pan set on a wire rack. After about 1 hour, you can place the whole pan in the refrigerator to help speed things up.

Whisk the icing ingredients together. Add more milk to thin out, if desired. Drizzle over cooled bars.

Lift the bars out of the pan using the edges of the parchment paper lining and place the whole thing on a cutting board. Slice squares with a sharp knife and, for neat squares, wipe the knife clean between each cut.

Cover and store leftover cherry pie bars (with or without icing) at room temperature for up to 2 days or in the refrigerator for up to 1 week.