Brush an 8 by12 lasagna dish with 2 tablespoons of chicken fat. In a medium skillet over medium heat, add 1 tablespoon of chicken fat and onions, and saute for 2 minutes, or until translucent. Let onions cool.
In a large bowl, mix potatoes, cooked onions, and dill together with remaining chicken fat and season with salt. Place mixture in lasagna dish and bake in the oven for 45 minutes to 1 hour, or until potatoes are tender in the center and crisp on top.
Remove from pan and layer top with smoked salmon. Cut into 10 equal size portions and serve.