This is what I used: https://thefoodcharlatan.com/buttermilk-ranch-dressing/

You can use dried herbs but I went all out with fresh herbs this time. Fresh dill is just absolutely divine.

I don’t keep buttermilk on hand so instead used this: https://www.amazon.com/Cultured-Buttermilk-Cooking-Baking-Powdered/dp/B0014D07BE . The recipe also has other substitution advice.