01 - Preheat oven to 425°F. Line a large sheet pan with parchment paper or lightly grease with cooking spray.
02 - Pat chicken breasts dry with paper towels. Rub evenly with olive oil, kosher salt, and black pepper. Arrange seasoned chicken in the center of the prepared sheet pan.
03 - Scatter pineapple chunks, red bell pepper pieces, yellow bell pepper pieces, and red onion wedges around the chicken on the sheet pan.
04 - In a small bowl, whisk together soy sauce, honey, rice vinegar, minced garlic, grated ginger, tomato paste, and crushed red pepper flakes if using.
05 - In a separate small bowl, mix cornstarch with water until completely smooth. Stir the cornstarch mixture into the sauce base until well combined.
06 - Drizzle half of the sauce evenly over the chicken and vegetables. Reserve remaining sauce for serving.
07 - Bake for 20 minutes until chicken begins to cook through and vegetables start to soften.
08 - Remove from oven. Brush chicken with more sauce from the pan and toss vegetables gently. Return to oven and bake another 8 to 10 minutes until chicken reaches internal temperature of 165°F and vegetables are tender.
09 - Let chicken rest for 5 minutes. Slice chicken and serve with roasted pineapple and vegetables. Drizzle with remaining reserved sauce and garnish with cilantro, sesame seeds, and green onions if desired.