Make the sauce: In a large bowl, stir together the ketchup, orange juice, sugar, chili paste and sesame oil. Set aside.
Make the fish: Season the salmon generously with salt and pepper, then drizzle with 2 tablespoons of the olive oil. Place the seeds on a plate and dredge the tops of the fillets in the sesame seeds to coat.
In an ovenproof skillet, heat the remaining 1 tablespoon olive oil over medium-high heat. Add the salmon, sesame seed side down, to the pan and sear, turning once, until golden brown about 3 minutes on each side.
Transfer the skillet to the oven and roast the salmon until cooked through, about 6 minutes.
Generously brush with the orange sauce and serve.
Notes
Cut back on the sugar for a less sweet version.
For a low FODMAP version, the amount of ketchup per serving falls between low to moderate in FODMAPS, so you can include it or substitute it with tomato paste. Most commercial chili paste contains garlic, so look for one that doesn't have garlic, or omit it from the ingredient list.