Wash and pat dry sea bass fillets. Drizzle with fish sauce, lemon juice and add salt and pepper to taste on both sides (optional)
Heat cast iron skillet over high heat until almost smoking. Reduce heat to medium high and add 1 teaspoon avocado oil. When hot add sea bass fillets, in a single layer. Cook for 4-6 minutes per side (without touching them) until browned and cooked through.
In a small bowl whisk together the sauce ingredients – lime juice, minced ginger, fish sauce, rice vinegar, agave, 1 teaspoon sesame oil, olive oil and sambal olek. Whisk until smooth.
Remove cooked fish and set aside. In the same pan cook the spinach in 1 teaspoon sesame oil until just wilted — about 1 minute.
To plate, first divide spinach onto four plates, sprinkle with sesame seeds, top with sea bass, and drizzle with sauce.