These small round peppers are stuffed with canned tuna and anchovies and then preserved in oil. The tart, vibrant flavors of the filling nicely balance the sweet heat of the peppers.
Finely chop tuna and anchovies. Combine with ⅓cup oil, bread crumbs, capers, parsley, salt, and pepper in a bowl. Stuff each pepper with tuna mixture. Transfer to reserved jar; pour remaining oil over peppers. Chill for at least 8 hours to marinate.