In a large mixing bowl, combine the ground turkey, breadcrumbs, milk, beaten egg, salt, black pepper, half of the ketchup, and chopped onion. Mix until well combined.
Transfer the mixture to a loaf pan and shape it into a loaf.
Spread the remaining ketchup over the top of the meatloaf.
Bake in the preheated oven for about 60 minutes, or until the internal temperature reaches 165°F (74°C).
Let the meatloaf rest for a few minutes before slicing and serving.
Notes:
Feel free to add your favorite herbs and spices to the meatloaf mixture for extra flavor.