Preheat oven to 425 F. Place half a thinly sliced sweet onion in a skillet or pan.
Dredge chicken thighs in rice flour, Kosher salt, and black pepper.
Place chicken thighs on top of onion, then drizzle with olive oil. Cook chicken, brushing the chicken thighs with teriyaki sauce. Garnish with sesame seeds and scallions. Serve immediately.