In a medium size bowl whisk together the marinade ingredients. Taste and adjust seasonings with more sea salt and spices. Add the chicken tenderloin and toss to coat well all over. Cover and refrigerate for a few hours.
Preheat a cast iron griddle on medium high flame. Add the chicken tenderloin and grill for about 1 or 2 minutes or so on each side, until nice grill marks form and the chicken is cooked through. About 3 to 4 minutes.
Transfer to cooked chicken to a platter and squeeze half a lemon over the top. Drizzle with the red pepper pesto and garnished with some fresh parsley leaves.
While the chicken is grilling caramelize the lemon slices. Spread the brown sugar on a small plate and dip the lemon slices in it to coat lightly. Grill them on the cast iron plate until golden caramelize, but make sure not to burn them or they will turn bitter.