Season salmon fillets on all sides with sea salt and black pepper.
Heat avocado oil in a deep 10-inch skillet over medium-high heat. Sear the salmon for 90 seconds per side until lightly golden; transfer to a plate (center will remain raw).
Reduce heat to medium. Add the diced shallot, garlic, and ginger to the pan and sauté for 2 minutes until translucent.
Pour in the coconut milk, fish sauce, and chili paste. Whisk to combine and bring to a gentle simmer.
Return the salmon fillets to the skillet. Cover with a lid and poach for 7 to 9 minutes, or until the internal temperature reaches 145°F (63°C).
Uncover the pan and stir in the baby spinach, cooking for 60 seconds until just wilted.
Remove from heat and stir in the fresh lime juice and lime zest.
Garnish with fresh cilantro and serve the salmon with the sauce ladled over the top.