Preheat the oven to 350 degrees F.
In a small saucepan, heat the orange liqueur. Turn off the heat and add the cranberries, making sure all the cranberries are submerged in the liquid. Set aside.
In a small bowl, mix together the cinnamon and the orange zest. Stir in the flour, baking powder, and salt. Set aside.
In a large bowl, mix together the eggs, butter, sugar, and vanilla. Add the dry ingredients and stir to combine. Add the apples, walnuts, and drained cranberries. Spoon the mixture into a lightly greased 8 by 8 by 2-inch glass baking dish or 8-inch cake pan. Bake until a wooden skewer inserted in the center of the cake comes out clean, about 30 minutes.
To serve, while still warm cut into squares or wedges and serve with ice cream.
Recipe courtesy of Giada De Laurentiis