In a saucepan, heat the oil. Add the garlic and onion and cook over moderate heat until softened, 5 minutes. Add the beef and chorizo and cook over moderately high heat, stirring, until browned, about 5 minutes. Add the ancho chile powder and cayenne and cook over low heat, stirring, until fragrant, about 1 minute. Add the tomatoes and their juices and simmer for 1 hour, stirring occasionally. Season the chili with salt and pepper.