Whisk together all of the sauce ingredients in a small saucepan. Set over low heat and stir occasionally until thickened, about 5 minutes.
Meanwhile, heat a large sauté pan over medium heat for 2 minutes. Add 1 tablespoon coconut oil and swirl to coat. Add bell peppers to pan and cook, stirring occasionally, until spotty brown on the edges, about 5-7 minutes. Remove peppers from pan and set aside. Add remaining 1 tablespoon coconut oil to the pan and swirl to coat. Place salmon skin-side down on the skillet and let cook (without moving) until bottom is golden brown on the edges, about 3-4 minutes. Using a spatula, flip each piece of salmon over and cook (without moving) until second side is golden brown on the edges, about 3 minutes. Place each piece of salmon on a plate and drizzle with teriyaki sauce. Serve with bell peppers, cauliflower rice (if using), green onions, and sesame seeds.