I eat this way more than I care to admit.
1/2 c pine nuts
6-8 oz. softened butter
1/2 c grated Parmesean or similar
Salt and pepper as needed
Toast pine nuts. Cook spaghetti. Toss drained noodles with butter. Add cheese and pine nuts. Top with salt and freshly ground black pepper.
Alternative: sub chopped fresh herbs for the pine nuts.