Position a rack in the upper third of the oven and preheat to 400°F (200°C). Lightly coat a 9×13-inch baking dish or a rimmed baking sheet with nonstick spray.
Beat the egg in a large bowl. Add the ground chicken, whole wheat panko, grated Parmesan, 1 tablespoon olive oil, dried oregano, garlic powder, onion powder, kosher salt, red pepper flakes, chopped parsley, and 1 tablespoon tomato paste.
Finely chop the spinach until in small bits, then add it to the bowl.
Using a fork or your hands, gently mix until the ingredients are evenly combined without compacting the meat.
Shape the mixture into 12 evenly sized meatballs and arrange them about 1 inch apart in the prepared dish so they don’t touch.
In a small bowl, whisk the remaining 1 tablespoon olive oil with the remaining 1 tablespoon tomato paste (it may not be perfectly smooth). Brush or spoon this mixture over the tops of the meatballs.
Bake the meatballs in the upper third of the oven for 18 to 22 minutes, until cooked through (internal temperature 165°F) and lightly browned.
Serve hot with tomato sauce and pasta, zucchini noodles, in buns for sandwiches, or with toothpicks as an appetizer.