Spiced squash, spinach and lentil soup

Name: Spiced squash, spinach and lentil soup
Cook time: 1 h 10 min
Total time: 1 h 10 min
Ingredients: 400g, peeled and cut into chunks butternut squash; 2 tbsp olive oil; 2 tsp, toasted, plus a few pinches to serve cumin seeds; 300g Puy lentils; 1.5 litres vegetable stock; 75g bulgar wheat; 200g, chopped baby spinach; 1/2, zested and juiced lemon; 4 tbsp natural yogurt