Preheat oven to 400 F. Mist a pie pan with nonstick cooking spray and set aside.
In a medium bowl, gently whisk the eggs to break up. Add the milk, nutmeg, Italian seasoning, garlic powder, salt, and pepper; whisk well and set aside.
Arrange the tomato slices in the bottom of the pie pan (it's okay if they overlap). Next, break off small bits of the mozzarella and arrange over the tomatoes then sprinkle with the basil leaves. Top the basil with the salmon, breaking off flakes of the salmon to distribute over the entire surface of the pan. Slowly pour the egg mixture over the salmon. If necessary, take a large spoon and press down on the filling ingredients to submerge under egg mixture.
Bake the quiche for 35-40 minutes or until completely set. Allow to cool for 5 minutes before slicing and serving warm.