Preheat your oven to 375 degrees Fahrenheit first.
Butter your baking dish generously to prevent sticking.
This step ensures easy serving later on.
Peel and core all three apples carefully now.
Slice them into thin, even pieces for cooking.
Arrange them nicely in your buttered baking dish.
Whisk eggs and sugar together until light yellow.
Add milk, vanilla, and rum to the mixture.
Pour in melted butter and mix it well.
Add flour and salt, whisking until completely smooth.
Pour batter over the arranged apple slices evenly.
Bake for 40-45 minutes until golden brown.
The center should be just slightly jiggly still.
Let it cool for 10 minutes before serving.
Dust with powdered sugar for a beautiful finish.
Serve warm for the best taste and texture.