Preheat your oven to 325 degrees.
Finely dice the onion.
Brown the ground beef and diced onion in a skillet and season with 1/4 teaspoon salt, 1/8 teaspoon pepper, sage, paprika, and garlic powder.
Place the toast in the bottom of a 9" x 13" baking dish.
Layer the cheese slices over the bread.
In a large bowl, whisk together the eggs, milk, 1/2 teaspoon salt, and 1/4 teaspoon pepper.
Stir in the browned meat and onions.
Pour the egg mixture into the baking dish over the bread and cheese.
Bake for 50 minutes.