The nibs of fenugreek will pucker your mouth, but the next wave of sweet coconut and spicy-hot chiles mellows out the obtrusive spice to make way for a well-balanced curry.
Combine the tamarind paste, salt, and turmeric in a medium-size bowl. Add the shrimp and toss to combine. Refrigerate, covered, for 30 minutes to 2 hours, to allow the flavors to meld. (Do not marinate too much longer, because the highly acidic tamarind and salt will break down the shellfish and turn its texture unappealing and rubbery.)