I’ve made many batches of swiss meringue buttercream but this time I added lemon juice at the end for a bright flavor addition per the recipe directions. I’ve been able to beat past the curdled stage when adding butter before however no amount of mixing was able to salvage the broken buttercream after adding the lemon juice (1 T). Did I add it too quickly or should I expect that adding acidity at this point will cause it to curdle no matter what? The cake was wonderful even with the curdled buttercream (covered it with chopped pistachio brittle) and when I called the bakery that published the cookbook, they wouldn’t answer my question. I’m wondering if next time I should just add some lemon curd at the end instead.
Would sincerely appreciate any advice as I plan to make the cake again soon.