Season the tenderloins evenly with the dried herbs including rosemary, oregano, parsley, paprika, basil, salt, and pepper. Make sure to season both sides. Set aside momentarily.

To a small bowl, zest the lemon, then add the chicken broth, olive oil, lemon juice (from the lemon you just zested), and whisk to combine. Set aside momentarily.

Spray the slow cooker liner with cooking spray if desired and then scatter the diced onions in the bottom of the slow cooker, and evenly sprinkle the garlic.

Place the seasoned tenderloins on top of the bed of onions and garlic, and drizzle the liquid broth and lemon mixture into the slow cooker. Tip - I pour a bit of it on top of the tenderloins, and the rest around the sides, so that the liquid doesn't "wash off" all the seasonings I just applied to the tenderloins.

Slow cook on LOW for 4-5 hours (my preference) OR on HIGH for 2-3 hours, or until the tenderloins are done. Tips - Turkey tenderloins are done when the internal temp reaches 165F as measured by digital thermometer. I pull my tenderloins when they're about 160F and allow them to rest on a cutting board for 5-10 minutes with a sheet of foil over the top, during which time the juices will redistribute and the internal temp will come up to a safe 165F. Don't overcook turkey tenderloins because they's so lean that they will be tough and dry if you do. And always rest the meat before slicing.

Optional Gravy - Make a slurry by combining 2 tablespoons cornstarch with 2 tablespoons water, add this to the juices in the bottom of the slow cooker, set to HIGH, place the lid, and allow it to thicken for 15 minutes, or as desired; check on it and stir it every few minutes.Alternatively, you can transfer the juices to a saucepan on the stove, add the slurry, and simmer over medium-heat for about 5 minutes, or until it has thickened as desired; whisk nearly continuously. Please see the links below as well if you want a more traditional gravy.

After the turkey has rested, optionally garnish with parsley, slice, and serve.