Chop chicken breast into cube sizes.
In a small bowl add the cubed chicken, soy sauce and toss to combine.
Set aside for 20 minutes to marinate.
In a baking pan, place the chicken with ½ cup flour and toss to combine.
In a small bowl add lemon juice, sugar, water, 2 tsp cornstarch and lemon zest. Mix to combine and then set aside for time being.
In a large skillet, add oil (about 3 cups) and heat on medium high.
Begin to add the chicken to the frying pan in batches.
Cook chicken until golden brown.
Once the chicken is cooked, transfer the pieces to a plate covered with a paper towel.
Continue until all the chicken is cooked.
When you finish all the chicken, drain the oil.
Place the skillet back on the stove, over medium to high heat.
Place the chicken back in the skillet and add the sauce.
Toss to combine.
Cook the chicken in the sauce, until thickened.