Preheat oven to 350 degrees F. Line sheet tray with parchment paper.
In a medium bowl, whisk together flour, baking powder, salt, brown sugar, and cinnamon. Cut butter into dry mixture using a pastry blender, fork, or your fingers until mixture resembles coarse sand.
Make a well in the dry ingredients. Add cream. Fold until almost combined. Add oats, cherries, and nuts. Fold until incorporated and all the dry has been hydrated.
Turn out dough onto a lightly floured surface. Pat into a circle about 1 inch thick. Using a sharp knife, cut circle into 8 equal slices.
To make the egg wash, whisk together the egg, salt, water, and heavy cream.
Transfer to prepared sheet tray. Brush each scone with egg wash and sprinkle with turbinado sugar. Bake for 20-30 minutes until golden brown. Let cool on sheet tray for at least 5 minutes. Enjoy warm or at room temperature.