1. In a large pan, fry 1⁄2 the onion in 1 tbsp oil for 3 minutes until soft. Add the garlic and jalapeno; cook for 2 minutes. Add the spice rub and sweet potato, tossing to coat. Tip in 200g tomatoes and 3 tbsp water; cover. Cook for 15-20 minutes, until the sweet potato is soft.
2. Meanwhile, sauté the remaining onion in 1 tbsp oil until soft. Add the coriander stalks, remaining 600g tomatoes and 200ml water. Cook over a medium heat until reduced by half, about 20 minutes.
3. Preheat the oven to 200 ̊C, gas mark 6. Stir the beans, salad onion, spinach and coriander leaves into the potato mixture until the spinach has wilted; season. Trim 3cm from the top and bottom of each tortilla; divide the mixture between them and roll up tightly.
4. Spoon 1⁄4 of the sauce into an ovenproof dish. Lay the tortillas on top, seam-side down. Brush with oil; bake for 15 minutes. Serve with the remaining sauce (reheated if necessary) and guacamole, if liked.