Make the chile sauce: In a saucepan, combine the dried chiles and onion. Cover with water, bring to a boil, then reduce to a simmer for 10–15 minutes until chiles are softened. Transfer to a blender with 2 ½ cups of fresh water, garlic, cumin, oregano, bouillon, salt, and pepper. Blend until smooth and set aside.
Prepare the beef: Season the beef chunks with salt and pepper, then lightly coat with flour. In a large skillet or pot, heat oil over medium-high heat. Working in batches, sear the beef on all sides until browned. Remove and set aside.
Build the stew: In the same pan, pour in the blended red sauce. Scrape up the browned bits from the bottom using a wooden spoon. Bring the sauce to a gentle simmer.
Simmer the beef: Return the seared beef to the pan, stir to coat in the sauce, and cover. Cook on medium-low (closer to low) for about 1.5 hours, or until the meat is fork-tender. Stir occasionally and adjust heat if needed to maintain a gentle simmer.
Serve: Serve warm with Mexican rice, refried beans, and fresh tortillas.