Preheat the oven to 375 degrees F. Spray a 9-by-13-inch baking pan with nonstick spray.
Butter the cut sides of the buns with half of the soft butter and sprinkle with the cinnamon sugar.
Melt the remaining butter in a medium saucepan over high heat. Add the golden syrup and brown sugar and cook until melted and smooth. Whisk in the marmalade and orange zest and juice and cook, stirring occasionally, for 2 minutes. Whisk in the heavy cream and salt. Pour the syrup mixture into the baking dish and scatter the almonds evenly over the top.
Put the buns in the syrup, cut-sides down, and bake until the syrup is bubbly, about 20 minutes. Remove to a cooling rack and let cool for 10 minutes. Invert (carefully!) onto a platter and eat.