Heat the avocado oil in a large skillet over medium-high heat.
Sear the beef round cubes on all sides until a golden-brown crust forms, then transfer them to the slow cooker.
Add the diced yellow onion, minced garlic, chopped carrots, and chopped parsnips to the slow cooker.
In a small jar or bowl, whisk together the beef broth, tomato paste, dried thyme, dried rosemary, sea salt, and black pepper.
Pour the liquid mixture over the beef and vegetables.
Cover and cook on the low setting for 7 to 8 hours until the beef is exceptionally tender.
Stir the stew gently before serving to combine the flavors and thickened sauce.