Add the onion to the pan, with extra oil if needed, and cook until softened. Stir in the garlic, cumin and chipotle paste, and cook for 1 min. Sieve the kidney beans, reserving the sauce. Add this sauce, along with the chopped tomatoes and a can full of water, to the pan. Stir well, then return the meat to the pan. Bring to a simmer, then cook, covered, for 2 hrs or until the beef is tender (or bake in the oven for 3 hrs at 160C/140C fan/gas 3).