In a mixing bowl, whisk together the egg white, cornstarch, and salt. Add the chicken and toss to coat. Let sit for 15 minutes at room temperature.
In a small saucepan, combine the pineapple juice, vinegar, Swerve, tomato paste, tamari, and ginger. Cook over medium heat until it begins to boil. Let boil gently for 5 minutes.
Heat a large skillet over high heat until hot – a drop of water should sizzle immediately when it hits the pan. Add 1.5 teaspoons of oil and swirl to coat the bottom of the pan. Let the oil heat for a few seconds. Add the chicken and spread into one layer. Let cook undisturbed for 2 minutes or until the bottoms are browned. Flip the chicken pieces and cook for another 2 minutes. Remove the chicken from the pan and put on a plate, leaving as much oil in the pan as possible. Add another teaspoon or two of oil, let it heat up, then add the bell peppers. Fry, stirring, for 1 minute. Add the pineapple and sauce to the skillet, cover, and let come to a simmer. Simmer for about 2 minutes or until the bell peppers have softened. Add the chicken back into the pan. Let simmer, uncovered, for 2 minutes or until the chicken is cooked through. Remove from heat and serve over rice, garnished with green onions and sesame seeds.