Preheat your oven to 350°F (175°C). Gather your ingredients while the oven heats.

In a stand mixer, cream together unsalted butter and both sugars until light and fluffy, about 3 minutes. Add the egg and vanilla extract, blending until well combined.

Gradually mix in flour, baking powder, and salt until the dough pulls away from the sides of the bowl.

Reserve about 2 cups of your dough for topping. Press the remaining dough evenly into the bottom of an 8x8 baking pan lined with parchment paper.

Bake the crust for 15 minutes, or until the edges are lightly golden. Let cool slightly.

In a mixing bowl, combine cranberries, sugar, cornstarch, orange zest, orange juice, and vanilla extract. Stir gently until cranberries are well coated.

Pour the cranberry filling over the pre-baked crust, spreading it gently. Crumble the reserved dough over the cranberry layer.

Bake for an additional 45 minutes, checking at 30 minutes and covering with foil if necessary.

Let the bars cool completely in the pan on a wire rack.

In a small bowl, whisk together powdered sugar, milk or cream, and vanilla extract until smooth. Drizzle over the completely cooled bars.

Slice into squares and enjoy!