Peel and roughly chop the tomatoes. Halve the onion and chop one half, then cut the other half in two. Dice the chorizo.
Cook the tomatoes and the two onion quarters in a saucepan over medium high heat. Add salt to taste and sugar. Cover and simmer until tender, about 30 minutes, then puree using an immersion blender (or in batches in a food processor).
Heat the olive oil in a large frying pan and cook the chopped onion till soft. Add the diced chorizo and cook for 10 minutes. Add the tomato sauce to the frying pan and stir well.
Meanwhile, boil the macaroni in plenty of salted water till al dente, about 8 minutes.
Toss the sauce together with the drained macaroni and serve straightaway. Enjoy!
You can use tinned whole plum tomatoes in a pinch.