In a small bowl, combine the cinnamon, coriander, cumin, paprika, salt and olive oil. Rub the mixture evenly over the pork tenderloins. Cover and refrigerate for at least 30 minutes or up to overnight.
Prepare a grill for high heat cooking. Place the tenderloins on the grill and cook until browned and nicely marked, 8 to 10 minutes. Turn the tenderloins and cook until a meat thermometer inserted into the center of each registers between 155 degrees F and 165 degrees F, 8 to 10 minutes longer. Transfer the tenderloins to a cutting board, tent with foil and let rest for 10 minutes. Slice and serve hot or at room temperature with Creamy Harissa Sauce.
Creamy Harissa Sauce:
In a small bowl, whisk together the yogurt, lemon juice, oil, harissa and garlic until combined. Season with salt and pepper.
*Harissa can be found at most grocery stores and in specialty markets. Substitute chili sauce for it if necessary.