Identify how you’re using sumac: sprinkle for finishing, mix into dressing/marinade, or bake for tang.
Pick the closest substitute from the list: lemon zest+juice for aroma, citric acid for the strongest control, vinegar for mellow sourness.
Apply using the listed ratio (or start at half the amount if you’re unsure), then taste and adjust for salt and sweetness.
If your substitute is wetter (juice/molasses/vinegar), reduce spillover by mixing into a sauce first or draining excess liquid before baking.
For baking, add the acidic substitute to wet ingredients and increase by ¼ ratio only if the tang is still missing.