Combine 1 tsp tamarind concentrate, 2 tsp cayenne pepper, 1/4 tsp black pepper, 1 tsp paprika, 1 tsp groun cumin, 1 tsp salt. Add 1 pound of deveined shrimps with the tail left attached. Mix until spicesd are distributed evenly over the shrimps.
In a glass or Corning ware dish with a glass lid, combine 3 TBL vegetable oil and 2 medium onions, sliced in thick half-rings. Cook in microwave for 6 to 8 minutes, until the onions are very cooked and looking glazed. Add the shrimps, cover and cook in microwave for 2 minutes, stirring once). You want to cook them until they are just barely done. Uncover and squeeze some lemon juice over them. Serve immediately.