To make white sauce:
In a medium bowl, mix together yogurt and mayonnaise. Gradually stir in fresh lime juice until consistency is slightly runny. Season with jalapeno, capers, oregano, cumin, dill, and cayenne.

I have made this several times and it is delicious. I have also substituted Miracle Whip for the Mayonnaise and it is very good.

I use about 1/3 of a Jalapeno chili, seeds and filament removed, diced up.

Capers are soft and hard to "mince." So I cut them in half.

Fish tacos are best with thin Cod or white fish, battered with beer batter and fried in deep oil on both sides until golden brown. Then drain, pat them dry with paper towels, break them into pieces.

I slaw some cabbage instead of lettuce. Place the cabbage and fish chunks in lightly fried corn tortillas (don't use oil! Fry them on a burner or right on a glass top range for just a half minute, both sides. You don't want them oily or stiff!)

Pour or spoon the white sauce on the fish and cabbage and eat! The tacos are soft ones, folded like a hard-shell taco.