Add olive oil, chopped onion, carrots, celery, and garlic into the Instant Pot.
Stir in the dry yellow lentils, ground turmeric, ground cumin, ground coriander, ground paprika, and cayenne pepper. Mix well to coat the lentils and vegetables with the spices.
Add the broth and undrained diced tomatoes to the Instant Pot.
Secure the lid on the Instant Pot and set it to "Manual" or "Pressure Cook" mode for 10 minutes. Ensure the steam valve is sealed.
Allow the Instant Pot to naturally release pressure for 10 minutes. Then, carefully quick-release any remaining pressure.
Open the Instant Pot and season the soup with salt and pepper to taste. Stir in lemon zest and juice and coconut milk. Add spinach if using. Adjust the spice levels if needed by adding more cayenne pepper for heat.
Optional: For a creamier texture, use an immersion blender to partially blend the soup, leaving some lentils and vegetables whole.
Ladle the Instant Pot Golden Lentil Soup into bowls. Garnish with fresh cilantro or parsley if desired. Serve with lemon wedges on the side for a burst of citrus flavor.