Preheat oven to 350 degrees F. Peel and thinly slice potatoes. Rinse in cold water and pat dry. Light butter a 9 x 13 inch casserole. Arrange a 1/3 of the potato slices in the bottom. Top with 1/2 the onions. Drizzle with a little melted butter, season with salt and pepper, and sprinkle on 1/2 the dill. Top with 1/2 the cheese slices. Top a 1/3 more potatoes, and then the rest of the onions. Drizzle with a little melted butter, season with salt and pepper, and sprinkle with remaining dill.
Arrange remaining potatoes on top. Season with a touch more salt and pepper and top with remaining cheese slices. Cover and bake 40 minutes, Uncover and bake 10-20 minutes more, until potatoes are cooked and top is golden.
Note: Havarti cheese slices are available in our deli. They're sold pre-packaged or by the slice.