Preheat the oven to 220°C / 425°F / Gas mark 7.
Lightly butter a baking dish and set aside.
Use a large bowl to mix the sugar and cinnamon.
Whisk the egg white in another bowl, then drop the plums first in egg white and then roll through the cinnamon sugar until generously coated to make a crust.
Space apart in the baking dish, then bake for 15 minutes or until the plums are crusty, cooked through and starting to turn juicy.
Poke in a cocktail stick or sharp knife and when it goes in easily, they are ready.