I’m not sure how much protein you can add but King Arthur Flour has a few blogs about what to do with sourdough starter beyond bread. * -https://www.kingarthurbaking.com/blog/2016/05/12/sweet-sourdough-baking -https://www.kingarthurbaking.com/blog/2014/07/27/excess-sourdough-5-tasty-ways-to-use-it-up * I’ve found that adding a few (2-3) scoops of unflavored protein powder never really hurts anything but I generally know what the consistency of cake/scones is supposed to look like.
In season tomatoes from the farmers market or garden. I went from “ew, raw tomatoes” to “omg, delicious”.