Add butter, molasses, and sugars to a small saucepan. Stir and melt over medium to med-low heat until combined. Set aside.
In a medium-sized mixing bowl whisk together flour, salt, baking soda, and ground spices. Be sure to mix and combine well.
Using the paddle attachment of a handheld or stand-mixer, mix the cooled molasses mixture on medium-high speed to incorporate air for volume - about 5 minutes.
Add the egg and mix until well-incorporated.
Mix in the vanilla.
Mix in half the flour-spice mixture, scraping sides of bowl with spatula if needed.
Mix in the milk.
Mix in remaining flour-spice mixture. Again scrape down the sides of bowl to ensure batter is well-combined.
Grease and line a 9x5 inch loaf pan with parchement paper. Pour in batter. Bake in preheated 350° oven 40-45 minutes or until an inserted toothpick comes out clean.
Remove from oven and allow to cool 5 minutes before removing from pan and placing on wire rack to cool completely.
Once the loaf cake is cool, drizzle orange icing on top.