Preheat oven to 400 degrees Fahrenheit
Add one cup marinara to bottom of 8x8 casserole dish and spread out evenly
Heat a medium skillet to medium heat and spray with non-stick cooking spray (I use spray olive or avocado oil)
Add ground turkey and garlic salt to skillet and cook until meat is no longer pink, stirring often
Add remaining 3 cups of marinara to cooked turkey and stir to combine
Add layer of lasagna noodles to casserole
Top noodles with half of the meat and marinara mixture and spread out evenly
Top the meat with 1 cup shredded mozzarella
Add another layer of noodles
Top with remaining meat and marinara mixture
Continue topping with 1 cup shredded mozzarella and 6 ounces feta cheese
Bake uncovered at 400 degrees for 40 minutes
Allow to cool for 5 minutes before serving