Prehead oven to 350 degrees F.
Melt butter in cast iron skillet or (melt butter and pour in 8x8 cake pan)
Put the eggs, milk, sugar, vanilla, and cinnamon in a large bowl. Use whisk to mix all the ingredients. note: when I add farm fresh eggs. I break them in a bowl first to make sure that they are okay. I break one open in the bowl, add it to the large bowl, and so on. I have another bowl handy for the egg shells.
Cube 12 slices of french bread and add to the bowl of wet ingredients.
Mix until all the bread is coated with the mixture.
Pour the batter/bread into the pan with the butter on the bottom.
Bake at 350 degrees F for 45 minutes. Longer if you desire your french bread drier and crispier on top.
Once done, remove to cool slightly