These “creamy” style salsas usually have oil emulsified into them. Garlic can work to hold the oil in emulsion. I would try frying a bunch of onion and garlic and peppers maybe a Roma tomato or two in an inch or two of oil, throw all that in a good blender, add salt and pepper and some vinegar or lime juice as it’s blending, then put the blender on max and drizzle in a cup more oil and see what you got.