Preheat oven to 300F degrees. Spray muffin tin with nonstick spray.
Toast bread on baking sheet in oven. Turn and bake until lightly browned, about 20 minutes.
In large bowl, whisk together eggs, buttermilk, pumpkin puree, brown sugar, pie spice, vanilla and salt. Add toasted bread. Cover with plastic wrap by pressing it directly to surface. Place a small plate inside bowl on top of plastic to weigh down bread as it soaks up custard. Let soak for 25 minutes. Transfer mixture to prepared muffin tins by spooning to 2/3 full.
Bake until firm, about 45 minutes, or until toothpick inserted comes out clean. Let cool 10 minutes and dust with confectioners' sugar before serving.