To make the topping: Mix the chopped apple, orange juice, lemon or lime zest and juice, and cardamom in a small bowl. Cover and set aside. Keep the cilantro and pumpkin seeds separate.
To make the soup: Heat a stovetop pressure cooker over medium heat or set an electric cooker to sauté. Add the onion and dry sauté for 3 minutes. Add the curry powder, squash, diced apple, stock, coconut milk, and salt.
Lock the lid on the cooker. Bring to high pressure; cook for 4 minutes. Let the pressure come down naturally. Remove the lid, carefully tilting it away from you.
Using an immersion blender, blender, or food processor, blend the soup until it is smooth and creamy. Add freshly ground black pepper to taste.
Just before serving, top each bowl with apple topping, cilantro, and pumpkin seeds.