Start by grating the Parmesan cheese and set it aside.
Zest the lemon to gather its fragrant outer peel.
In a saucepan, combine the double cream and lemon zest, heating gently over low heat.
Once the cream is warm, add the grated Parmesan and stir until it melts and creates a smooth sauce.
If the sauce is too thick, add a splash of pasta water to reach your desired consistency.
Season the sauce with salt and pepper according to your taste.
Serve the pasta topped with the creamy lemon sauce, and garnish with chilli flakes and lemon slices.
