Heat a skillet with a tablespoon of butter over medium heat.
Combine dry ingredients: flour, salt, cinnamon, and sugar into a shallow dish.
Add eggs and mix into dry ingredients. It will be thick, but by doing it this way, you'll get all the dry ingredients to combine easier than if you add the buttermilk first.
Mix in the vanilla extract. Next, slowly add in the buttermilk, making sure to stir well. You'll want to make sure to scrape any bits of flour or other ingredients off the bottom.
After everything is mixed together well, dip a slice of bread into the egg mixture and then flip the bread so the other side is coated as well.
Place the bread covered in egg mixture into the skillet. If there is enough room, add another egg mix covered slice of breads to the skillet. Cook until the bottom is a golden brown about 2-4 minutes, then flip the bread over and cook the other side. I like to add in another dollop of butter when I flip the bread over. This helps the French toast not burn.
Once the French toast is done, place it on a plate. And continue cooking the rest of the bread slices as you did the first one.