• Preheat the oven to 350°F with a rack in the center. Line a 9x13 baking pan with parchment paper and set aside.

Shortbread Crust

• In a large bowl, whisk together the flour, sugar, and salt until combined. Add the butter and vanilla, and use a pastry blender to cut in the butter until the dough stick together when you pinch some between your fingers.
• Pour the dough into the prepared baking pan, and press down using your fingertips. Bake for 25-30 minutes until browned at the edges. Set the crust aside to cool while you prepare the filling and streusel, leaving the oven on.

Cherry Pie Filling

• In a medium saucepan, add the cherries, flour, sugar, and water. Stir to combine. Cook over medium heat and bring to a simmer. Cover and let cook undisturbed for 2 minutes.
• Uncover, and continue simmering for an additional 5 minutes until the mixture thickens slightly.

Streusel Topping

• In a small mixing bowl, whisk together the flour, oats, brown sugar, and salt until combined. Add in the butter and mix with a spoon or your hands until uniform and somewhat crumbly.

Cherry Pie Bars

• Once the crust has cooled for about ten minutes, spread the cherry pie filling on top, even distributed any large cherry pieces. Using your fingertip to crumble the streusel, distribute it evenly over the top of the cherry filling.
• Bake the bars for 15-20 minutes, until the streusel appears dry and slightly browned. Let the bars cool in the pan on a trivet for 1-2 hours before serving.
• Use the parchment paper (and a friend) to carefully remove the bars from the pan and place onto a flat surface. Cut with a chef's knife into 24 squares. Serve room temperature or warmed with whipped cream or vanilla ice cream.

Simple Glaze (optional)

• In a small bowl, combine the sugar and half the water. Add the remaining water slowly until you reach a thick drizzling consistency. Drizzle in diagonal stripes over the cooled cherry pie bars, before cutting.