Heat the oven to 425F and arrange rack in the upper third. Set a rack on a foil lined baking sheet; set aside.
Combine flour, 1 teaspoon of the salt, and 3/4 teaspoon of the pepper in a shallow bowl, mix until well combined; set aside. Combine Panko, 1/3 cup of the parsley, 3 tablespoons of the olive oil, 1 1/2 teaspoons of the salt, and all the lemon zest in a separate shallow bowl, and toss until evenly combined; and set aside. Whisk together eggs and cheese in a shallow bowl until evenly combined; set aside.
To coat chicken, dredge a piece in the flour mixture and shake off excess. Then dip into egg mixture, let excess drip off, and finally roll in the breadcrumbs, pressing to adhere as necessary. Place chicken piece on baking sheet and repeat with remaining chicken.
Bake until coating is golden and crispy, juices of chicken run clear when poked, and internal temperature is 160degreesF, about 40 to 45 minutes. Meanwhile, combine remaining 1/2 teaspoon of the salt, 1/4 teaspoon of the pepper, remaining 1/3 cup of the parsley, 1 tablespoon of the olive oil, all the red onion, all the tomatoes, and the lemon juice in a non-reactive bowl and toss to combine. Serve chicken topped with a bit of the tomato mixture.
*If you can't find skinless, bone-in chicken, by it with skin on and pull it off. To get a better grip, grasp skin with a paper towel and pull!