Heat oil in a large pot, stir in onion and garlic. Cook for 3-4 minutes until onion has softened. Add spices and cook a further minute. Stir in tomato paste.
Add stock, water, lentils, pumpkin and sweet potato. Bring to the boil, reduce heat and simmer for 30 minutes until lentils, pumpkin and sweet potato are tender. With a handheld blender puree until smooth. Season well.
Pour cream into a piping bag (if using). Snip 3mm off the end of the bag. Squeeze a blob of cream into the center of the bowl and 3-4 rings around the center blob. With a skewer or a toothpick, drag through the rings of cream from the center towards the edge of the bowl to create a spider web pattern. Garnish with toasted pepita seeds.