Carefully cut the bell pepper, white onion, and pineapple into 1-inch cubes and set aside in separate bowls.

In a large bowl, combine the cubed chicken with minced garlic, grated ginger, chopped onion, light soy sauce, and Shaoxing cooking wine. Mix well and let it marinate for an hour.

Add half of the corn starch to the marinated chicken and mix until evenly coated. Then coat with remaining corn starch for crispy texture.

Heat oil to 350°F in a deep skillet or wok and fry the battered chicken in batches for about 3 minutes until golden brown.

In a large pan, heat a tablespoon of oil and toast the tomato paste for 1-2 minutes. Add white vinegar, water, sugar, and soy sauce, bring to a simmer for 5 minutes.

Gradually pour in the cornstarch slurry while stirring constantly, until the sauce thickens to a glossy consistency.

Add bell pepper, pineapple, and white onion to the sauce and cook for 1 minute. Fold in the fried chicken pieces to coat.

Serve immediately over fluffy white rice.