In large saucepan or stockpot heat the oil or butter. Add pasta and saute until golden, stirring frequently and being careful not to burn. Stir in chiles and cook for 2 minutes longer. Meanwhile, combine tomatoes, garlic, onion, water and salt in a blender. Puree until smooth. Add tomato puree and stock to browned pasta. Cook over medium-low heat until the noodles soften and the flavors meld, about 15 minutes. Serve hot with the sliced avocado and cilantro as garnish.