In a large bowl, whisk together the eggs, milk, sugar, vanilla extract, cinnamon, and salt until well combined.
Pour the egg mixture into a shallow dish or pie plate wide enough to fit a slice of bread.
Working with one slice at a time, place the challah in the custard. Let it soak for 2 to 3 minutes per side, until it has absorbed the liquid but is not falling apart.
Set a large nonstick skillet or griddle over medium heat. Add 1 tablespoon of butter and let it melt and sizzle.
Carefully place 2 to 3 soaked bread slices in the hot skillet, ensuring not to overcrowd the pan.
Cook for 3 to 4 minutes per side, until deep golden brown and crisp. The center should be cooked through, reaching an internal temperature of 160°F (71°C) to ensure the egg is fully cooked.
Transfer the cooked French toast to a wire rack or a baking sheet in a warm oven (200°F / 95°C) to keep warm.
Wipe the skillet clean with a paper towel, add more butter, and repeat with the remaining bread slices.
Serve warm with your favorite toppings like maple syrup, fresh berries, or a dusting of powdered sugar.