Cook pasta: Place a large pot of water on the hob and let it come to a boil. When the water starts to boil, add salt generously and cook the spaghetti according to the package's instructions.
Chop: In the meantime, chop the bell peppers into small cubes and cut the green onions into thin rings.
Saute: Heat the oil in a large cast-iron or nonstick pan and cook the peppers and the green onions for about 5 minutes until they soften.
Chop: In the meantime, remove the seeds of the tomatoes and chop them into small cubes. Grate the garlic cloves.
Whisk: Mix the milk, cream cheese, vegetable broth, and tomato paste in a bowl and whisk carefully until smooth. Set aside.
Caramelize: Add the sugar to the pan with the vegetables and let caramelize slightly for about 1 minute.
Combine: Add the tomatoes, garlic, and cream cheese sauce to the vegetables in the pan. Add salt and pepper to taste and chili powder if you wish to have a hotter dish.
Cook: Let cook gently until the vegetables are soft and the sauce thickens.
Serve over spaghetti with some green salad on the side.