In a medium bowl, combine cubed chicken breast with baking soda, salt, fresh orange zest, and ground black pepper. Toss the chicken to ensure it's evenly coated in the marinade. Allow it to sit for 10 minutes.

While the chicken is marinating, place a non-stick skillet over medium-high heat and add coconut oil or butter. Allow the oil to heat up for about 2 minutes until it’s shimmering but not smoking.

Add the marinated chicken to the hot skillet in a single layer. Cook for approximately 5-7 minutes, or until the chicken turns golden brown. Flip the pieces and cook for an additional 3-5 minutes until cooked through.

Once the chicken is golden and fully cooked, reduce the heat to medium. Stir in the grated onion and minced garlic, cooking for 2-3 minutes until aromatic.

In a small bowl, whisk together fresh orange juice and cornstarch until smooth. Pour this mixture into the skillet with the chicken, along with the soy sauce or tamari. Stir vigorously for 2-3 minutes as the sauce bubbles and thickens.

Once the sauce reaches a glossy, thick consistency, remove the skillet from heat. Toss the chicken in the sauce until every piece is well-coated. Garnish with additional orange zest before serving warm.