Preheat the oven to 425°F and then use a meat tenderizer to pound the chicken breasts into a 1-inch thickness.
To make the rub, mix the olive oil, lemon juice, oregano, paprika, cumin, mustard powder, salt, and pepper together.
Completely cover the chicken breasts in the rub.
Lay the chicken into a casserole dish or onto a baking tray lined with parchment paper. Place the dish into the heated oven to bake for 15 minutes, or until the internal temperature reads 165°F. Allow the chicken to rest for 5 minutes before serving.