I can't speak for the doujin artist, but in the context of the story? This is one of Wakatsuki's culinary triumphs she's handed to her crush. Sempai is glaring at her, and she's clueless as usual saying, "Oh, it's nothing anyone could have produced a wonderful cake like this, sempai, it's filled with all my feelings for you!" Because Wakatsuki doesn't realize a burnt pile of ingredients isn't a cake masterpiece.