Preheat an oven. Flanken can either be left whole or each rib can be cut in half for smaller portions. Season flanken ribs on all sides generously with Kosher salt and black pepper.
Heat a large dutch oven over high heat until very hot. Add canola oil then sear ribs until browned on both sides. Transfer seared flanken to a plate.
To the hot pan, add onion and carrots, then cook, stirring often. Add minced garlic and cook more, then stir in tomato paste.
Pour in red wine, then use a spatula to scrape any brown bits off the bottom of the pan. Allow wine to cook down, then add beef stock and ground cinnamon. Stir to combine.
Return seared flanken ribs to the pan, then add prunes and rosemary. They will cook down and shrink a bit as they cook!
Cook until rib meat is tender and pulls gently away from the bones. Discard rosemary stems. Allow to cool slightly before serving.