Using a non-reactive container (stainless steel, glass, or heavy plastic), combine apple cider, vinegar, molasses, red pepper flake and cracked black peppercorn. Mix well. Add pork tenderloin. Cover container and refrigerate for 6-8 hours or overnight. Remove from marinade and drain well. Refrigerate until sauce is made.

Combine onion, garlic, molasses, tomatoes, stock, red pepper flake, vinegar, dates, and salt and pepper in a large pot. Allow ingredients to come to gentle simmer and reduce liquid by half. Allow mixture to cool slightly, and then carefully puree mixture in a blender until smooth. You will have to do this in two or three batches. Return pureed mixture to the heat and simmer until desired consistency. Adjust seasonings and serve warm.

Season pork with salt and pepper, and grill pork over a medium-high heat. Pork is done when internal temperature is 145 degrees to 150 degrees. The pork should rest 10 minutes before slicing.