While the potatoes are in the oven, prepare the tomato paste sauce. Heat 2 tablespoons of sunflower oil in a small pan. Add the grated onion and garlic and sauté until softened. Then add the tomato pastes, chili powder, and black pepper and sauté for
2 minutes. Add the juice of half a lemon and the finely chopped parsley, then remove from the heat.