in a 9X13 baking dish, whisk together eggs, milk, 1/4 cup sugar, vanilla, and salt.
Arrange bread in dish in a single layer; let soak 15 minutes. Turn bread over; conver and regrigerate until most of the liguid is absorbed, at least 30 minutes and up to overnight.
Preheat oven to 350. Brush a rimmed baking sheet with butter. With a spatula, carefully transger soaked bread to sheet. Bake until French toast is set in center and lightly browned on the bottom, 25-30 minutes.
Meanwhile, in a medium bowl, combine raspberries and remaining 1/4 cup sugar, mashing lightly with a fork.
Remove French toast from baking sheet with a thin metal spatula; serve with raspberry sauce and , if desired, sausage.