Preheat oven to 350°F Grease a 9X13 pan and set aside.
Cook the pasta in a large pot. Drain and set aside.
Melt butter in a deep skillet, and saute onions for 5 minutes. Add garlic, mushrooms, salt and caraway seeds. Cook for about 5 minutes, or until mushrooms are cooked. Stir in spinach, remove from heat, and add to pasta.
Mix in cottage cheese, buttermilk, dill, black pepper and half the cheddar. Spread in prepared pan, sprinkle with remaining cheddar and sunflower seeds , and bake uncovered for 20-30 minutes.
I served this hot, but it's pretty tasty at room temperature for lunch the next day, too.