Preheat oven to 300°F / 150°C.
Peel garlic cloves and place in a small baking dish.
Pour olive oil over the garlic so it’s fully covered.
Add rosemary.
Roast for 40–50 minutes until soft and golden.
Transfer garlic + some of the oil to a blender.
Add butter, tomato paste, parmesan, parsley, salt & pepper.
Blend until smooth and creamy.
Cook pasta until al dente. Save some pasta water.
Warm sauce in a pan.
Add pasta + a splash of pasta water.
Toss until silky and glossy.
Finish with extra parmesan, parsley & black pepper
