Preheat the oven to 350°F (175°C).

Lightly grease the loaf pan with cooking spray or olive oil.

Sauté the chopped onions over medium heat until soft and translucent, about 5 minutes.

In a large mixing bowl, combine ground turkey, breadcrumbs, sautéed onions, milk, egg, ketchup, Worcestershire sauce, garlic powder, thyme, salt, and pepper. Mix until just combined.

Transfer the mixture to the prepared loaf pan and shape it into a loaf.

Spread a thin layer of ketchup on top of the meatloaf.

Bake in the preheated oven for about 1 hour, or until the internal temperature reaches 165°F (74°C).

Remove from the oven and let it rest for 10 minutes before slicing.