Remove the stems and seeds from the dried ancho and guajillo chiles. Heat a small skillet over medium heat and toast the chiles for about 2 minutes until they become fragrant
Be careful not to burn them. Once toasted, place the chiles in a bowl and cover them with hot water for about 20 minutes to soften.
After the chiles have softened, drain the water and blend them with 1 cup of beef broth in a blender until smooth. This chile paste will be the flavor foundation of your Texas chili.
In a large pot or Dutch oven, heat 2 tablespoons of vegetable oil over medium-high heat. Season the beef cubes with salt and pepper, then sear them in batches to avoid overcrowding the pot. Cook each batch until browned on all sides, then remove the meat and set aside.
In the same pot, add the chopped onions and cook for about 5 minutes until softened. Add the minced garlic and cook for another minute until fragrant.
Stir in the cumin, paprika, oregano, garlic powder, and cayenne pepper. Cook the spices for 1 to 2 minutes to enhance their flavors.
Return the seared beef to the pot, along with the chile paste and the remaining beef broth. Stir in the tomato paste if you're using it. Bring the mixture to a boil, then reduce the heat to low. Cover the pot and let the chili simmer for about 2.5 to 3 hours, stirring occasionally. This slow-cooking method allows the flavors to develop fully.
In the final 30 minutes of cooking, mix 2 tablespoons of masa harina with a little water to create a slurry. Stir it into the chili to thicken the sauce. If the chili becomes too thick, you can add more beef broth or water.
Taste the chili and adjust the salt, pepper, or cayenne for heat. Let it simmer uncovered for the last 10 minutes to slightly reduce and intensify the flavors.
Ladle the chili into bowls and garnish with your favorite toppings like shredded cheese, chopped onions, or fresh cilantro. Serve with cornbread or tortilla chips for a complete meal.