Chop the garlic and salt in a mortar and then add the other spices and the onion and process the mixture into a thick sauce by adding the remaining ingredients (if necessary in a different container). Finally, process the whole thing with the hand blender and ideally let it steep overnight.
The Salsa Gaucha from Ybarra served as a model for this sauce. Unfortunately this sauce is not identical to the original, but I think it at least comes close. I had to estimate the quantities because I didn`t measure everything.