Trim fat and outer skin from beef. Cut into 1 inch 1 1/2 inch pieces. Toss in seasoned flour to coat, then brown in hot oil or fat. Add roughly chopped onions. Sprinkle in any remaining seasoned flour. Add hot stock and tomato puree to the pan and bring to the boil. Transfer to a large casserole, cover and place in a slow oven (300 F, gas mark 2). Peel carrots and potatoes. Leave whole or cut in half (lengthwise for carrots) if very large. Add to casserole and sprinkle with salt. Re-cover and cook until meat is very tender 3 to 4 hours.