Slow-Cooker Pork and Sweet Potatoes (healthy comfort food!)

pork tenderloin, cut into ¾-inch thick pieces (excess fat removed)

 3 cups raw, sliced sweet potatoes **

 1/2 cup chopped onion **

 1/2 cup chopped green bell pepper

 1 can (14.5 ounce size) diced tomatoes

 2 tablespoons brown sugar

 1/2 teaspoon cinnamon

dried parsley

 1/8 teaspoon black pepper

Parsley for garnish (optional)