In a small bowl, whisk the sour cream and mayonnaise until well blended.

Squeeze the juice from one lime half into the fish taco sauce mixture, then whisk thoroughly. You'll want the consistency of a pourable, creamy salad dressing. If still too thick, add more lime juice from the other half. If too runny, add sour cream.

Add all of the spices, whisking to mix thoroughly. Add the capers, minced pepper and cilantro, and whisk thoroughly.

Cover the bowl with wrap and refrigerate the Sauce for at least one hour - the longer the better. Serve chilled. Spoon white sauce over fish tacos, or add into taco salads or rice bowls.