Add the onion, beef, garlic, salt, pepper, paprika, cayenne, broth, and tomato paste to a 6-quart slow cooker pan.
Gently mix everything together.
Cover, and cook on HIGH for 3 hours. You can also cook on LOW for 7 hours.
When done, whisk the cornstarch with water until smooth. Stir the slurry into the beef mixture. If you cooked the goulash on high, the stew should thicken immediately. If you cooked it on low, or if it doesn't thicken right away, set the slow cooker to high, cover, and cook for 15-30 more minutes, until the stew thickens.
Serve immediately.
