1. Using the saute function, heat the oil in the pressure cooker. Add the fennel, onion, and salt, and cook until the vegetables have just softened, 5 minutes. Add the squash and coriander and cook, stirring occasionally, until the vegetables are starting to turn golden at the edges, 7 to 10 minutes.
2. Add the stock, cover, and cook on high pressure for 20 minutes. Let the pressure release naturally.
3. Using an immersion blender directly in the pot or transferring the soup to a blender, puree the soup with the lemon zest until smooth. Season with salt, pepper, and lemon juice to taste. Serve garnished with the fennel fronds, cilantro, and a drizzle of olive oil.