1Heat olive oil in a large pot over medium-high heat. Working in batches, brown the beef cubes on all sides, about 3 minutes per batch. Transfer to your slow cooker as you go.
2Add diced onion to the pot and cook until softened, about 3 minutes. Stir in garlic and tomato paste, cooking for another minute to deepen the flavors.
3Pour in beef broth, scraping up any browned bits from the bottom of the pot, then transfer to the slow cooker.
4Add crushed tomatoes, kidney beans, and black beans to the slow cooker.
5In a small bowl, combine chili powder, cumin, paprika, oregano, salt, black pepper, and cayenne. Stir the spice blend into the slow cooker.
6Cover and cook on low for 8 hours or on high for 4 hours. The chili is ready when the beef is tender and the flavors have melded together.
7Taste and adjust seasonings if needed. Serve hot.