If you haven’t already, make some jasmine rice (or white rice) for serving.
Season the salmon. Pat the salmon filets dry with a paper towel, then season on both sides with 1 tsp Kosher salt and ¼ tsp black pepper.
Pan-sear the salmon. In a large skillet or wok, heat 2 Tbsp canola oil over medium-high heat. When very hot, add the salmon fillets and cook undisturbed for 4 minutes. Carefully flip, then cook additional 3-4 minutes more. Remove from the pan and set aside.
Sauté the veggies. To the same pan, add thinly sliced onion, diced red bell peppers, and orange bell peppers, Cook for 3 minutes, stirring occasionally. Add 4 cloves chopped garlic and 2 tsp ginger paste then cook 1 minute more. Deglaze the pan with 2 Tbsp soy sauce, 2 Tbsp rice wine vinegar, and 2 tsp sesame oil, scraping the bottom of the pan to release any brown bits.
Make the coconut curry sauce. Add 1 can of coconut milk, 3 Tbsp Thai red curry paste, 1 Tbsp brown sugar, and 2 Tbsp fish sauce. Use a spatula to help break up the curry paste. Add 1 (5oz) bag of fresh baby spinach and the juice of 1 lime, then stir well until the spinach has wilted. Taste and adjust seasoning, adding more lime juice, soy sauce, or salt, as needed.
Assemble, then serve. Either return the salmon to the pan with the curry sauce or plate the salmon over white rice and spoon the curry sauce on top. Either way, garnish with lime wedges, fresh cilantro, fresh basil, sliced scallions, chopped peanuts, and Thai red chile (if using).