Heat the oil in a large skillet over medium-high heat.
Season the beef with salt and pepper, then toss with almond flour.
Add the beef to the skillet and cook until browned on all sides then transfer to a slow cooker.
Reheat the skillet over medium-high heat, then pour in the broth.
Scrape up the browned bits, then whisk in the wine and tomato paste.
Bring to a boil, then pour into the slow cooker.
Add the mushrooms and onion, then stir everything together.
Cover and cook on low heat for 4 hours until the meat is very tender. Serve hot.