Place oven rack 4-5 inches from heat. Turn oven on to Broil. Prepare sheet pan by lining with foil.
To a large bowl, add ground turkey, taco seasoning, crushed tortilla chips, and beaten egg. Grate the onion over the bowl to catch all the juice. Mix everything together using your hands until it is combined. Do not overmix.
Form into four equal patties, pressing down the middle of each so they are slightly thinner in the middle. Arrange on prepared sheet pan.
Broil about 6 minutes (or until golden brown), flip over, cook for another 2-3 minutes, add cheese slices, and cook for one more minute or until cheese is melted and burgers are cooked through to 165°F.
Add to buns, top as desired and serve immediately.