Heat the oil and cook the onion and garlic until soft and golden.
Add the kidney beans and their liquid and stir in the tomato paste and spices and cook for a few minutes.
Add the lime juice to the kidney bean mixture. Take the pan off the heat and when it has cooled a little, process the mixture until it is a bumpy puree. When it is cool, arrange in small bowls and sprinkle over the reserved lime zest.