Cook the fettuccine

• Bring a pot of generously salted water to a boil.
• Cook the fettuccine until al dente, following the package directions.
• Reserve at least 1 cup of pasta water, then drain without rinsing.

Soften the garlic and onion

• Heat the olive oil in a large skillet over medium-low heat.
• Add the sliced garlic and cook until fragrant.
• Add the diced onion and cook until soft and translucent.

Build the tomato base

• Add the cherry tomatoes and cook, gently pressing some with the back of a spoon to release their juices.
• Add the tomato paste and Calabrian chili paste and cook, stirring constantly.
• Add half a cup of the pasta water and stir to combine.

Make the sauce creamy

• Lower the heat and slowly add the heavy cream, stirring constantly, then simmer gently.
• Season with salt and black pepper.
• Gradually add the cheddar, followed by the Parmesan, stirring until melted and smooth.
• Add more pasta water, a splash at a time, until the sauce is silky.

Toss the pasta

• Add the fettuccine and toss, adding more pasta water if needed.
• Turn off the heat, add the butter and toss until glossy.
• Add a squeeze of lemon juice and toss again.

Finish and serve

• Finish with freshly grated Parmesan and chopped parsley.
• Add extra Calabrian chili paste or chili flakes if you like it spicy.