Heat a tablespoon of olive oil in a large pot over medium heat. Add the beef cubes and cook until browned on all sides, about 5-7 minutes. Remove and set aside.
In the same pot, add a bit more olive oil if needed, then add the diced onion and bell pepper. Cook until softened, about 5 minutes.
Add the minced garlic and chili powder to the pot. Cook for another minute until fragrant.
Return the browned beef cubes to the pot. Add the diced tomatoes and kidney beans. Stir to combine.
Bring the chili to a simmer, then reduce the heat to low. Cover and let it cook for about 1 hour, stirring occasionally, until the beef is tender and flavors are blended.
Season to taste.
Serve hot.