Preheat oven to 350°F (175°C) and grease a loaf pan.
In a large bowl, combine stuffing mix with 1/2 cup broth and let sit until absorbed.
Add ground turkey, egg, onion, celery, salt, pepper, sage, and garlic powder. Mix gently until combined.
Transfer mixture to loaf pan, press gently, and smooth the top.
Bake 45–50 minutes, or until internal temperature reaches 165°F (74°C).
While baking, make the gravy glaze: melt butter in a saucepan, whisk in flour, and cook 1–2 minutes. Gradually whisk in broth until smooth. Season with onion powder, garlic powder, salt, and pepper, then simmer 5–7 minutes until thickened.
Let the meatloaf rest 10 minutes after baking. Remove from pan, pour glaze over the top, and slice to serve with extra glaze on the side.