2In a large baking dish, add sliced onions, olive oil, balsamic glaze, salt, and pepper. Toss until evenly distributed. Cover with foil and bake for 1 hour and 10-15 minutes, or until soft, sticky, and sweet.
3Slice the top of a garlic bulb, drizzle with oil, wrap in foil, and bake for 1 hour, or until golden, sticky, and soft.
4Cook pasta in salted boiling water until al dente. Drain, reserving some pasta water.
5Once the baking dish is hot, squeeze roasted garlic into the caramelized onions and mash. Mix in sun-dried tomatoes, mascarpone, and a splash of pasta water.
6Stir in the cooked pasta, parmesan, and basil. Add more pasta water to thin the sauce if needed. Season with salt and pepper to taste.