Preheat your oven to 350 degrees F. Grease an 8-inch x 8-inch baking dish and set aside. (see note)
Beat butter and sugar together with a hand mixer until smooth. Add the beaten eggs to the bowl and mix well.
Add the drained pineapple and stir to combine. Add the cubed bread and mix everything really well.
Pour the casserole mixture into the prepared baking dish. Bake uncovered for 45 minutes.
Remove from the oven and cut into 6 pieces. Serve warm or cold.
Video
Notes
I removed all of the crusts from the bread, but my mother-in-law does not. Both ways work great!
I used an 8-inch x 8-inch pan for a thicker casserole, but my mother-in-law uses a 9-inch x 13-inch for a thinner casserole and to last longer with a bigger crowd