Heat oven to 325F. Slather butter on one side of each of the bread slices. Lay them out in a buttered baking dish so the bread slices cover both the sides and the bottom. Beat the eggs, mix together sugar, salt and cinnamon and stir into the eggs, then slowly incorporate the milk into this mixture until well-blended. Add vanilla and raisins. Pour this over the bread. If you have used large slices of bread and have some leftover, push them down into the milk mixture until they soak up liquid, then turn them over and push them down again to soak. Let this sit for about 15 minutes. Cover and bake for 30 minutes, then uncover and continue to bake for 30 more minutes. The pudding will come out of the oven very bouffant and will slowly fall.