Make the sauce. Heat the oil in a saucepan, add the onion and cook for 5 minutes until softened. Stir in the garlic and cumin and cook for 30 seconds. Add the tomatoes and chipotle paste and bring to the boil, then season. Reduce the heat and simmer for 15 minutes, topping up with water if needed.
Meanwhile, mix together the pumpkin purée, feta and coriander in a bowl, then season. Place a couple of teaspoons of the mixture on to each tortilla and roll up.
Spread about one-third of the tomato sauce over the base of a large baking dish. Place the tortillas in the baking dish, seam-side down. Spoon over the remaining sauce and scatter with the Cheddar.
Bake in a preheated oven, 200°C (425°F), Gas Mark 7, for 15–20 minutes until golden and bubbling.