Preheat oven to 425°F. Place a cast iron skillet over medium-high heat and allow it to fully preheat until very hot.
Prepare the glaze. Whisk together all glaze ingredients in a small bowl and set aside.
Season the salmon. Pat dry and lightly season with kosher salt. Add avocado oil to the hot skillet, then place the salmon skin-side up and sear for 2–3 minutes, until a golden crust forms.
Flip and glaze. Turn the salmon over, reduce heat slightly if needed, and spoon glaze over the top (reserve some for serving). Transfer the skillet to the oven and roast for 6–7 minutes, or until the salmon is just cooked through.
Rest and serve. Remove from the oven and let rest for a few minutes. Spoon over reserved glaze and finish with cilantro, green onions, and optional sriracha.