Preheat the oven to 350F and line a 9x13 pan with parchment paper. Lightly spray the parchment with nonstick baking spray. 

In a large bowl, whisk together the flour and powdered sugar. Add the melted butter and mix to combine. 

Transfer the dough to the prepared pan and press it gently into the bottom– you just want to smooth the dough into an even layer, not compact it. 

Bake for 15-18 minutes or until the crust is golden brown. 

Remove the crust from the oven and let it cool while you make the other layers.

Add the cranberry sauce, sugar, lemon juice, lemon zest, and cornstarch into a microwave safe bowl. Heat for 1 minute and then whisk until no large lumps remain. Spread the mixture evenly over the shortbread crust.

In a large bowl, whisk together the sugar and flour. Next, add the eggs and vanilla and which to combine. 

Finally, add the lemon juice and whisk to combine. 

Carefully pour the lemon layer over the cranberry layer, making sure not to disturb the cranberry layer. 

Bake for 30-35 minutes or until the lemon layer is set and no longer jiggles when the pan is gently shaken. 

Allow the bars to cool completely to room temperature and then transfer them to the fridge to chill (at least 4 hours). 

When ready to serve, use the parchment to lift the bars out of the pan. Slice them into your desired size and dust with powdered sugar, if desired. 

Store any leftovers in an airtight container in the fridge for up to three days.