Cook the spaghetti in a large pot of generously salted boiling water until al dente. Reserve ½ cup cooking water, then drain the pasta.

While pasta cooks, heat olive oil in a large pan over low heat. Add garlic and tomato paste; cook for about 30 seconds.

Stir in butter until melted, then whisk in the paste until dissolved.

Pour in double cream and bring briefly to a simmer. Stir in Parmesan until melted and sauce becomes silky smooth.

Add the drained spaghetti and ¼ cup reserved pasta water; toss until pasta is fully coated in sauce and sauce thickens. Add more pasta water if needed to loosen texture. Finish with black pepper.

Serve immediately, garnished with extra Parmesan and a drizzle of olive oil if desired.