Preheat the oven to 180°C/350F/gas mark 4. Chop the squash into medium sized cubes and place on a baking tray. Cut the red onion into rough chunks and add to the tray with the squash. Sprinkle over the chili flakes, paprika, salt and pepper and 1 tablespoon of oil, mix with your hands until the squash and onion is coated nicely. Roast in the oven for 30-35 minutes until soft, set aside.
Add the garlic to the sour cream with a little salt and pepper and stir, set aside. Put the lentils in a large mixing bowl and add the mustard, lemon and 1 tablespoon oil. Mix until the lentils are coated. Add the spinach and feta to the bowl and the cooled squash and onion, mix until all combined. .
Serve in large bowls topped with the cashews and dollops of sour cream