Preheat the oven to 300 degrees F (150 degrees C). Cut bread into ½-inch cubes and divide onto 2 sheet pans.

Bake in the preheated oven until bread is completely dry, and cubes have just started to take on a very light golden color, 30 to 45 minutes. Let bread cool, then transfer into a large bowl.

Melt butter in a large skillet over medium-high heat. Add onions and salt, and cook, stirring, until onions turn translucent and start to take on a little bit of golden color, 3 to 5 minutes.

Add ground turkey, and cook and stir for a few minutes, while crumbling the meat into small pieces with a spatula. Continue to cook, stirring occasionally, until onions and turkey take on some brown color, a few more minutes. Stir in black pepper, nutmeg, garlic powder, poultry seasoning, and cayenne, and cook and stir for 1 minute more.

Add flour, and cook for about 2 minutes. Pour in broth, raise the heat to high, and bring to a boil. Cook until gravy thickens slightly, then continue to cook for about 3 minutes. Stir in celery, and boil until celery begins to lose its crunch, about 3 minutes more. Taste for seasoning, and adjust if necessary. Turn off the heat.

Preheat the oven to 375 degrees F (190 degrees C).

Pour gravy carefully over dried bread cubes. Add rosemary and parsley, and stir until thoroughly and evenly combined, and stuffing has cooled slightly. Pour in beaten eggs, and stir again.

Transfer stuffing into a deep 9x13-inch casserole dish, and distribute evenly, but leave the surface rough, with plenty of cracks and crevices.

Bake stuffing in the preheated oven until the top is beautifully browned, about 40 minutes. Let rest about 10 minutes before serving.