Make the Cranberry Filling:

Cup of Yum
1. To a medium stockpot with high sides, add the cranberries, optional orange zest, orange juice, granulated sugar, and bring to a boil over high heat, stirring often to incorporate the sugar.
2. Once mixture has come to a boil, reduce the heat to medium low, add the corn starch, stir to combine, and allow mixture to simmer for about 15 minutes. While it simmers, make the bars.

Make the Bars:

1. Preheat oven to 350F. Line an 8-inch square pan with aluminum foil and spray with cooking spray; set aside.
2. To a large, microwave-safe bowl add the butter and heat on high power to melt, about 1 minute.
3. Add the sugars, vanilla, and whisk to combine.
4. Add the flour, oats, optional salt, and stir to combine. Mixture will have some larger, well-formed crumble pieces as well as some sandier, dryer bits.
5. Set 1 heaping cup mixture aside to be sprinkled on later as crumble topping.
6. Transfer remaining mixture to prepared pan, and using a spatula or your fingers, hard-pack the mixture to create an even, smooth, flat crust.
7. Add the cranberry filling over the crust making sure there’s complete coverage but leave a 1/4-inch bare margin around the edges. Tip – The cranberry filling will burn if it’s touching the edges of the pan and will also stick like crazy.
8. Evenly sprinkle with the reserved heaping 1 cup crumble topping mixture. Tip – Before sprinkling, I squeeze the mixture in my palm to encourage bigger crumble pieces to form.
9. Bake for about 30 to 35 minutes, or until edges are set and center has just set and is lightly golden browned.
10. Place pan on a wire rack and allow bars to cool for at least 2 hours before slicing and serving.