Flavored with anise, lemon zest and vanilla. They taste good on first bite but leave a very bitter after taste.
How much lemon zest does it call for? Did you get the pith in the zest? That can sometimes be bitter.
I thought if that but I tried to be careful about that. Would too much anise extract make it bitter?
One of your dry ingredients may have spoiled. Or, maybe you added too much baking soda/powder, which is bitter. That's a shame, they ARE beautiful....
Would cream of tartar make them bitter? It was called for as an ingredient. I’ve only ever used it when whipping egg whites.