Line a 9x9 inch pan with parchment paper and preheat the oven to 350°F.
In the bowl of a stand mixer fitted with the paddle attachment or a large mixing bowl using a hand mixer, cream together the softened 1/2 cup salted butter and 1/4 cup sugar until light and fluffy, approximately 2-3 minutes.
Stir in the 1/2 teaspoon vanilla extract and mix again. Add the 1 cup flour and mix until dough has formed.
Press the dough onto the bottom of the prepared baking pan to form an even layer.
Bake the crust for 20-25 minutes until the top is lightly browned. Remove and allow it to cool for 10 minutes. Leave the oven on.
Lemon & Cranberry Layers:
In a medium mixing bowl, whisk together the 4 eggs, 1 1/4 cup sugar, 1 tablespoon fresh lemon zest (about 1 lemon) and 1/2 cup fresh lemon juice (about 4 lemons).
Sift the 1/2 cup flour and add to the mixture. Mix until the lemon mixture is smooth.
Top the still-warm crust with the 1 cup canned whole berry cranberry sauce. Make sure the crust is still warm, this helps the layers bind.
Smooth the lemon layer on top of the cranberry sauce and bake for another 30-35 minutes until the lemon layer has set, but is not browned. Let the bars cool completely and then chill in the refrigerator for a minimum of 4 hours, but up to overnight.
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Notes
Refrigerator: Wrap bars tightly with plastic wrap or aluminum foil, or keep them in an airtight container for up to 1 week.Freezer: Freeze cranberry lemon bars for up to 3 months in a freezer-safe container or freezer bag.