In a large bowl combine buttermilk, salt, garlic and onion. (can also add in red pepper or hot sauce!)
Submerged chicken into mixture.
Cover and refrigerate for 4 hours or overnight.
Stir in remaining spices (feel free to cut back on the spices by half if you don't like extra seasoned chicken. I always taste my flour to make sure it's seasoned well.)
Remove the chicken from the buttermilk, letting most but not all of the excess buttermilk drip off.
Place the chicken into the flour mixture and with the other hand, coat the chicken completely with the flour.
Place coated chicken on a plate and continue until all the chicken is coated heavily with flour.
Let the chicken rest until the flour looks as though it is getting absorbed (very important to prevent the coating for sliding off)
When it's time to fry the chicken, heat oil in a cast iron skillet. The oil is hot enough when a leftover clump of flour fries gently.
Gently lower the tenders into the hot oil a few at a time. The oil should be steady with lots of calm bubbles. It should not be sputtering, smoking or popping out of the pan. Reduce the heat if needed.
Cook until underside is golden and then flip and continue cooking until that side is golden and crispy. (Cooking times will vary based on thickness.)
Remove from oil and let drain on a plate lined with paper towels or a cooking rack.