1. Place rack in center of oven; preheat to 425°. Line a rimmed baking sheet with foil. Place a wire rack on top and mist rack with cooking spray. Place flour in a shallow bowl. Place eggs in a separate shallow bowl and lightly beat. Combine panko and Parmesan in a third shallow bowl.
2. Cut tenderloin into 8 pieces and pound each to a 1/4-inch thickness between 2 sheets of plastic wrap or parchment. Sprinkle cutlets with salt, dredge in flour, dip in egg and coat in panko mixture.
3. Place cutlets on rack and bake until cooked through and just beginning to turn golden around the edges, 15 to 20 minutes. Remove baking sheet from oven and set oven to broil. Spread 1 Tbsp. marinara sauce on each cutlet and sprinkle with mozzarella. Return to oven and broil, watching carefully, until cheese is bubbling and golden, 2 to 3 minutes. Serve immediately.