Mix together the paprika, chili powder, coriander, 1 teaspoon black pepper and 1 teaspoon salt in a small bowl. Sprinkle the steaks on both sides with the spice mixture. Refrigerate for 1 hour.
Heat the olive oil in a large skillet over medium-low heat. Add the onions and sprinkle with salt and pepper. Cook, stirring occasionally, until soft and slightly golden, 10 to 15 minutes. Add the garlic, tomato paste and pepper flakes, and cook for 2 minutes. Stir in the beef broth, hot sauce and Worcestershire. Cook until thickened, about 5 minutes. Keep warm.
Prepare a grill or grill pan for medium-high heat.
Grill the steaks for 3 to 4 minutes per side for medium rare. Let rest for 5 minutes. Serve topped with the onion sauce.