The copycat recipe embodies what people love about the Starbucks loaf — a tender crumb, a bright lemon flavor, and thick icing that seeps into the top and runs off the sides.
Mattison's copycat loaf is bite-for-bite, similar to the version sold at Starbucks, and it's all thanks to the inclusion of one special ingredient: buttermilk.
Buttermilk is a fermented milk with a tangy scent and higher acidity levels than standard milk. When baking soda is mixed with an acid, it reacts to leaven the batter or dough.
The copycat lemon loaf is tender and moist with a tall rise. The buttermilk also imparts some of its tangy flavor to the loaf, which harmonizes with the sugar and lemon.