How to Make It
Working over a medium bowl, grate the tomatoes on the large holes of a box grater until only the skin remains in your hand; discard the skin.
In a small saucepan, heat the oil. Add the onion and cook over moderately low heat, stirring, until softened, about 5 minutes. Stir in the sugar, vinegar and tomato pulp and cook, stirring occasionally, until very thick, 12 to 15 minutes. Stir in the lime juice and a pinch of salt and season generously with pepper. Transfer the jam to a bowl and let cool completely.