In a wide-based pan over a medium heat, caramelise the red onions in 75ml of the olive oil for 15 minutes or until they turn golden and soft. Add a little fine salt, the garlic and spices and continue to cook for 2-3 minutes. Add the tomato purée and cook for another minute.
Add the butter beans and sherry vinegar and reduce the liquid by half over a medium heat. Turn the heat off. Add the piquillo peppers and the remaining olive oil and season with sea salt flakes (kosher salt) to serve.