Heat oven to 350 F. Trim fat from tenderloin and slice into 1 1/2 inch rounds. Spread walnuts on a baking sheet and toast about 8 minutes; put on a plate to the side.
In a small bowl, stir together cumin, 1/2 tsp salt, 1/2 tsp paprika. Rub spice mixture into pork and set to the side.
Sauce: in a food processor, combine walnuts and garlic. Add roasted peppers, vinegar, remaining 1 1/4 tsp paprika, cayenne and 1/4 tsp salt. Whirl until smooth. **Add liquid from bell pepper jar if thinner texture desired.
Heat large pan or wok to medium heat and coat with cooking spray. Working in batches, add pork rounds in a single layer and cook until brown about 2 minutes per side. Use a meat thermometer to ensure an internal temperature of 140F.
Remove to plate and spoon sauce on each pork round.