Heat large skillet or griddle over medium-low heat.
In a large bowl, whisk eggs, milk, pumpkin, brown sugar, vanilla, pumpkin pie spice, and cinnamon together until well-combined.
Pour the pumpkin mixture into a large shallow dish.
Add the bread to the dish and turn to coat both sides.
Add butter to the skillet and swirl to coat.
Place the coated bread in the skillet.
Cook for about 3 minutes, or until golden brown.
Flip the bread and continue cooking until the other side is also golden brown, about 2-3 minutes.
Repeat with remaining bread.
Notes
Milk - any milk, from skim to whole milk, will work. However, whole milk will make for richer French toast. Nondairy milk, like almond milk, will also work.
Pumpkin puree - Be sure to use pumpkin puree, not pumpkin pie mix.
Brown sugar - Light or dark brown sugar will work. Dark brown sugar will give the French toast richer flavor.
Pumpkin pie spice - If you can't find pumpkin pie spice, you can make your own with this easy recipe.
Bread - Thick-sliced bread, like Texas toast, works well. Other thick-sliced sandwich breads, like Artesano breads, also work well.