Preheat your oven to 350°F (175°C). Grease the 9x13 inch baking pan or line it with parchment paper for easy removal.
In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy. This will take about 3 minutes.
Add in the flour, salt, and baking powder. Mix until combined.
Reserve 1 cup of this mixture and set it aside. Press the remaining mixture firmly into the bottom of the prepared baking pan to form a crust.
In another bowl, whisk together the egg, vanilla extract, brown sugar, orange juice, and orange zest until smooth.
Fold in the cranberries gently, making sure they are evenly distributed.
Pour the cranberry mixture over the crust in the baking pan, spreading it evenly.
Crumble the reserved crust mixture over the top of the cranberry layer.
Bake in the preheated oven for 30 minutes, or until the top is lightly golden and the filling is set.
Remove from the oven and let the bars cool in the pan on a wire rack.
Once completely cool, cut into 12 bars with a sharp knife.