Whisk together buttermilk, garlic powder, onion powder, salt, paprika and pepper in a large bowl. Add the chicken tenders to the buttermilk chicken marinade and stir to coat all of the chicken.
Cover and marinate in the fridge for at least 1 hour or up to 6 hours.
Heat 4 inches of vegetable oil in a deep frying pan or Dutch oven to 300 degrees F / 180 degrees C over medium heat.
While the oil comes up to temperature, remove the chicken from the marinade, reserving 1 ½ cup of the marinade and adding half cup of flour then stirring until combined.
Add the remaining half cup of flour to a shallow bowl and the breadcrumbs to a separate shallow bowl.
Dredge the chicken tenders one at a time in the dry flour then the buttermilk mixture and finally dip it in the breadcrumbs. Gently press more breadcrumbs on to coat the chicken completely.
Fry the chicken tenders (3 to 4 tenders at a time) for 5-6 minutes or until they turn a light golden color and the internal temperature is 165 degrees F / 74 degrees C when checked with a meat thermometer.
Drain buttermilk fried chicken tenders on a cooling rack to keep them crispy.
Serve with ketchup or your favorite dipping sauce and garnish with freshly chopped parsley if desired.