Roast the tomatoes and garlic

• Halve the tomatoes and place them on a baking tray.
• Coat generously with olive oil, salt and pepper, then turn them cut-side down.
• Add the garlic cloves and roast at 180 °C.

Soften the onion

• Dice the white onion.
• Fry it in olive oil until soft and starting to brown.

Add the tomato paste

• Add a generous squeeze of tomato paste to the onion.
• Cook for a few minutes to remove the bitter taste.

Cook the spaghetti

• Salt the pasta water heavily and bring it to a boil.
• Add the spaghetti and cook until al dente.

Blend the sauce

• Put the onions, roasted garlic and roasted tomatoes with all their juices into a blender and pulse until smooth.
• Add the basil and pulse again so the leaves are chopped but not mushy.

Simmer the sauce

• Pour the sauce into the pan and season again with salt and pepper.
• Simmer for a couple of minutes.

Combine pasta and sauce

• Add the spaghetti to the sauce and mix well, adding pasta water to loosen and silk it up.
• Grate the parmesan over the top and mix with a little more pasta water.

Serve

• Serve with more parmesan and a big glug of olive oil.