In a medium non-metallic bowl, combine brown sugar, ketchup, vinegar, reserved pineapple juice, soy sauce, salt and 2 teaspoons of the cornstarch. Whisk until dissolved and set aside.
In resealable plastic bag, combine flour and remaining cornstarch.
Add chicken to flour mixture; seal bag and shake to coat.
Transfer chicken to cutting board and lightly spray both sides with cooking spray.
In large skillet over medium-high temperature, heat 1 teaspoon canola oil; swirl to coat the bottom of skillet.
Cook chicken on one side for 4 minutes or until golden on the bottom.
Turn chicken and pour in remaining oil, spreading as much as possible.
Cook another 4 minutes until golden and chicken is no longer pink in the center.
Transfer to a plate and cover to keep warm.
To the same skillet, add carrots, onion and red bell pepper. Cook on medium high heat, stirring occasionally, for 2 or 3 minutes or until tender-crisp.
Make a well in center of vegetables.
Pour pineapple juice mixture into the well; cook 1 or 2 minutes stirring the juice mixture occasionally until thickened.
Add pineapple chunks; stir vegetables and pineapple chunks into the sauce.
Add chicken and cook 2 or 3 minutes more, stirring occasionally, until heated through.