Preheat the oven to 400 degree F. Use 2 tablespoons of butter to grease a large baking dish. (9x13 or a smaller deeper dish.)
In a large bowl, whisk together the flour, sugar, baking powder, cinnamon and salt. In a separate bowl, whisk the milk, remaining butter (melted) and 2 eggs.
Mix the wet mixture into the dry mixture until well combined. Then stir in the blueberries, withholding a large handful for the top.
Pour the batter into the baking dish and sprinkle the remaining berries over the top. Bake 40-60 minutes (depending on the depth of the dish) until a toothpick comes out clean.
Meanwhile, whisk together the ingredients for the rosewater sauce and set aside.
To serve, scoop the warm pudding onto plates and drizzle with rosewater sauce.