Trim any excess fat from the chicken breasts and cut into serving-size pieces.
In a medium bowl, whisk the egg and lemon juice until combined, then add the chicken pieces, toss to coat, cover, and refrigerate for 30 minutes.
Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper or foil and set aside.
In a shallow dish, combine the breadcrumbs, grated Parmesan, lemon zest, garlic powder, salt, and pepper; mix well.
Remove chicken from the egg mixture, let excess drip off, then press each piece into the breadcrumb mixture to coat both sides; place coated pieces on the prepared baking sheet and lightly spray the tops with cooking spray.
Bake for 15 minutes, flip the pieces, then bake an additional 10 minutes until the crust is golden and an instant-read thermometer inserted into the thickest part reads 165°F (74°C).
Serve warm with fresh lemon slices.
