1. Cook pasta according to package directions in boiling salted water; drain well. While pasta is cooking, melt 2 Tbsp butter in a large skillet. Add butternut squash, onion and garlic and cook over medium heat for 10 to 12 minutes or until squash is tender; remove from heat.
2. Melt remaining butter in a large skillet over medium heat. When butter starts to foam, cook for 2 minutes more or until it turns golden brown, stirring to keep if from burning. Add to vegetable mixture with lemon juice and sage; season to taste with salt and pepper.
3. Toss with hot cooked pasta and place on 4 serving dishes. Sprinkle with cheese and pine nuts.