Heat olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Add the ground beef, break it up with a spoon, and cook undisturbed for a few minutes to develop a deep brown crust. Continue cooking until fully browned, then use a slotted spoon to transfer the beef to a separate bowl, leaving the rendered fat in the pot.
Reduce the heat to medium. Add the chopped onion and bell pepper to the pot and sauté for 5-7 minutes, stirring occasionally, until they have softened. Add the minced garlic and cook for another minute until fragrant.
Add the chili powder, cumin, smoked paprika, oregano, salt, and pepper to the pot. Stir constantly for about 60 seconds to bloom the spices in the fat. Stir in the tomato paste and cook for another minute.
Pour in about a half cup of the beef broth to deglaze the pot, using your spoon to scrape up all the browned bits from the bottom.
Return the browned beef to the pot. Add the remaining beef broth, the crushed tomatoes, and the diced tomatoes. Stir everything together until well combined. Bring the mixture to a boil, then immediately reduce the heat to low.
Cover the pot and let it simmer for at least one hour, or preferably 90 minutes for deeper flavor. Stir every 15-20 minutes to prevent sticking.
In a small bowl, whisk together the masa harina with 1/4 cup of warm water to create a smooth slurry. Pour this slurry into the chili and stir well.
Increase the heat to medium and let the chili bubble gently for another 5-10 minutes, uncovered, until it has thickened to your desired consistency.
Taste and adjust the seasoning with more salt or cayenne if needed. Let the chili rest off the heat for 10 minutes before serving with your favorite toppings.