In a bowl, whisk together the orange zest, orange juice, brown sugar, rice vinegar, soy sauce, Sriracha, ginger, garlic powder, and dissolved cornstarch. Whisk until there are no white streaks left from the cornstarch.
Towel dry the pieces of chicken, as it's important to remove excess moisture for even browning. Cut into bite-size pieces. In a large nonstick pan, heat oil over high heat until hot. Add chicken and kosher salt. Cook and stir until chicken is just cooked through, about 2 minutes. Transfer cooked chicken to a bowl and cover to keep warm.
In now-empty pan, add the orange sauce mixture. Cook and stir over medium heat until thickened, 30 seconds. Return the cooked chicken back to pan, along with any accumulated juices. Toss to coat chicken.