Preheat oven to 350 degrees F (175 degrees C). Lightly butter an 8x8 inch baking pan.
Line bottom of pan with bread cubes. In a large bowl, beat together eggs, milk, salt and vanilla. pour egg mixture over bread. Dot with butter; let stand for 10 minutes. Sprinkle cinnamon over the top. Bake in preheated oven about 45 to 50 minutes, until top is golden.