Combine brown sugar, paprika, oregano, salt, garlic powder, onion powder, chili powder, black pepper, cayenne, and 2 teaspoons of the olive oil in a small bowl. Stir well, then rub this mixture all over the chicken breasts with your hands or with a fork.
1 Tablespoon brown sugar, 2 teaspoons paprika, 2 teaspoons dried oregano, 1 teaspoon kosher salt, 1/2 teaspoon garlic powder, 1/2 teaspoon onion powder, 1/2 teaspoon chili powder, 1/4 teaspoon black pepper, 1/8 teaspoon cayenne pepper, 1 Tablespoon olive or avocado oil, 4 thin-sliced chicken breasts