Preheat oven to 350 degrees F (175 degrees C). Grease a 9 1/2-inch fluted cake pan (such as Bundt®).
Whisk flour, baking powder, pumpkin pie spice, and salt together in a bowl.
Beat sugar, pumpkin, vegetable oil, and eggs together in a bowl until smooth. Slowly beat flour mixture into pumpkin mixture until batter is smooth. Fold in cranberries and walnuts. Pour into prepared cake pan.
Bake in the preheated oven until a toothpick inserted in the center of the cake comes out clean, about 35 minutes.