Heat the oil in a large frying pan, add the onions, garlic, chili and ginger and cook, stirring occasionally for a few mins until all the aromas are released and the onion is softened but not colored.
Add the curry powder and season with salt then cook, stirring for a further 2 minutes.
Add the tomatoes, with most of their juice and cook for about 3 minutes Add the beans and cook for a further5 mins or until the beans are warmed through and the sauce is thickened.
Add the lemon juice and serve hot garnished with cilantro.