Heat some oil in a small, heavy saucepan. Add the onion and fresh chillies and fry over a medium heat until softened. Add the fajita paste, garlic, chilli flakes, and paprika, and fry gently for a couple of minutes. Add the tomatoes and a handful of coriander, and bring to the boil. Season accordingly with salt/pepper, reduce the heat, and simmer until step 2 is done.