Gather all your ingredients to ensure a smooth preparation.
Cube the gluten-free bread and butter one side of each cube. Arrange half in a greased baking dish, buttered side up, and sprinkle with raisins or currants if using.
In a large mixing bowl, whisk the eggs, then add the milk, heavy cream, sugar, vanilla, cinnamon, and salt. Mix until smooth.
Pour the custard mixture over the bread layers, ensuring all pieces are soaked. Let sit for 15-20 minutes.
Preheat the oven to 350°F (175°C) and bake for 40-45 minutes until golden brown and set.