In a medium bowl, mix together fresh cilantro, freshly squeezed orange juice, brown sugar, soy sauce, creamy peanut butter, minced garlic, grated ginger, and a dash of red pepper flakes until everything is thoroughly blended.
Place the pork tenderloins in a glass baking dish and pour the flavorful orange marinade over them. Cover and let it marinate in the refrigerator for a minimum of 1 hour, or up to 8 hours or overnight for deeper flavor.
Preheat your oven to 375°F (190°C) and prepare a baking sheet by lining it with aluminum foil.
Remove the marinated pork tenderloins from the dish and place them on the prepared baking sheet, setting aside the marinade for later use.
Bake in the preheated oven until the pork is cooked through and no longer pink in the center, about 30 to 35 minutes. Ensure the internal temperature reaches 145°F (63°C) using an instant-read thermometer.
While the pork is roasting, take the reserved marinade and combine it with chicken stock in a medium saucepan. Bring the mixture to a boil, allowing it to bubble for 2 minutes, then lower the heat and let it simmer for an additional 5 to 7 minutes. Remove from heat and keep it warm.
Once cooked, slice the tenderloins into 1/4-inch thick pieces and arrange them on a serving platter. Drizzle the warm sauce over the sliced pork before serving.
