Heat a cast iron skillet or grill pan over high heat.
Set aside 2 tsp of ranch seasoning for use in the aioli.
Add all burger patty ingredients to a large bowl and combine using a wooden spoon or dough whisk. (ground turkey, diced red onion, dried basil, ranch seasoning, black pepper)
Prepare the patties: Use a ¼ cup measuring cup to scoop uniform sized patties. Use your hand to form into a ball, then gently press down to make the patties. Aim for ¼” thick, 6” patties. *Tip, make the middle of the patty slightly thinner than the edges to help the patty to hold its shape as it cooks. It will shrink slightly once cooked*
Generously spray the cast iron with non-stick cooking spray and add 3-4 patties at a time depending on the size of your cooking pan.
Cook for 4 minutes, then flip the patties and cook for 4 more minutes.
Once 8 minutes have passed, add a slice of cheese to the top of each patty and cook for 1 more minute.
Repeat until all patties are cooked, then add the buns cut side down to the grill pan and cook for 2 minutes to lightly toast.
Prepare aioli. Add all ingredients to a food processor or blender and puree.
Assemble the burgers.
Add a piece of butter lettuce to the bottom bun and top with the burger patty.
Then add a dollop of avocado aioli to the top bun and enjoy!