Slice the chicken breast horizontally into thin cutlets and pound them to an even thickness of about half an inch.
In a shallow bowl, whisk the egg until smooth. In a separate shallow bowl, combine the almond flour, sea salt, black pepper, and garlic powder.
Dip each chicken cutlet into the egg wash, letting any excess drip off, then dredge thoroughly in the almond flour mixture until well-coated.
Heat the olive oil in a large non-stick skillet over medium-high heat.
Place the chicken cutlets in the skillet and cook for 3 to 4 minutes per side, or until the crust is golden brown and the chicken is cooked through.
Remove the chicken from the pan and immediately sprinkle with fresh lemon zest while the crust is still hot.
In a small bowl, toss the fresh arugula with the lemon juice and serve it as a refreshing bed for the crispy chicken cutlets.