Stir cornstarch, garlic powder, onion powder, salt and pepper together in a medium bowl. Add chicken tenders; toss until coated. Stir tamari (or soy sauce), honey, garlic, chile-garlic sauce and vinegar together in a small bowl; set aside.
Heat oil in a large nonstick skillet over medium heat. Add the chicken; cook, flipping once, until the chicken is browned and crispy and an instant-read thermometer inserted in the thickest portion registers 165°F, 10 to 12 minutes.
Add the sauce to the pan, turning the chicken to coat; cook over medium-low heat until the sauce is slightly thickened, about 30 seconds. Remove the chicken from the pan; drizzle with any remaining sauce. Garnish with scallions, if desired.
