Preheat the oven to 350°F and spray/grease a 2-quart casserole dish.
Place the bread cubes in a large bowl.
To scald the milk, heat it until it's steamy, melt the butter in it, and then pour this mixture over the bread cubes. Stir. Pour in the pineapple, cornstarch, eggs, sugar, and vanilla and stir everything together until the eggs and sugar are well-blended with the bread mixture. Pour the mixture into the prepared dish and sprinkle with cinnamon.
Bake for about 45 minutes, or until the center is loosely set.