1. Preheat the oven to 400°F. Slice the top off the garlic head, drizzle with 1 tablespoon olive oil, wrap in foil, and roast for 35 to 40 minutes until soft and golden. Cool slightly, then squeeze the cloves out.

2. Bring a large pot of salted water to a boil and cook the pasta until al dente. Reserve 1/4 cup pasta water, then drain.

3. In a large skillet over medium-low heat, add the remaining 1 tablespoon olive oil and the butter.

4. Add the roasted garlic and mash it into the butter and oil until smooth and fragrant.

5. Pour in the heavy cream and stir until combined.

6. Add the Parmesan cheese gradually, stirring until melted and smooth.

7. Stir in the lemon zest, lemon juice, salt, black pepper, and red pepper flakes if using.

8. Add the reserved pasta water a little at a time until the sauce reaches a silky consistency.

9. Toss the cooked pasta into the sauce until evenly coated.

10. Finish with chopped parsley and serve hot with extra Parmesan if desired.