So, there's something I usually prepare for myself. It's pretty straightforward (since I have 0 knowledge and skills in cooking). I add roasted red peppers (from a can), white cheese, onion, garlic & olive oil in a food processor and blend them to a smooth puree.   However I have a new friend who is vegan and I want them to try this, so I was wondering what can I use to replace the white cheese?  I suppose the cheese is kind of necessary & I cannot just skip it because it "softens the pepper's strong flavor". 
Loin or tenderloin is a very lean cut of meat and should not be cooked in a slow cooker.  Slow cookers are better suited to cuts of meat with high amounts of connective tissue, like pork shoulder or chuck roast, that turns into gelatin as it cooks for a long time.  IMHO, tenderloin should be grilled or broiled just until the center is 145° or so. Then rested and sliced.  Good luck! 