Preheat the oven to 300 degrees F (150 degrees C). Grease and flour a 10-inch tube pan.
Combine dates, walnuts, flour, sugar, and baking powder in a large bowl. Stir in egg yolks until combined.
Beat egg whites in a clean, large glass or metal mixing bowl until stiff peaks form. Fold whites into date mixture until no streaks remain. Spoon into the prepared pan.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 90 minutes. Let cool in the pan for 10 minutes, then turn out onto a wire rack to cool completely.