Marinate Shrimp - Whisk oil with 3 tablespoons of tamarind sauce, add in shrimp and mix well. Let marinate for 5-10 minutes
Cook Shrimp - Grill or broil shrimp on high heat.To broil shrimp: preheat oven to 500ºF and place a baking sheet one level above the center of the oven. Once oven reaches 500ºF, remove the baking sheet and place shrimp onto the hot baking sheet. Switch oven to broil and let broil for 10 minutes. Half way through broiling, flip each shrimp.
Prepare Salad - Place spinach in a large bowl, drop in sliced onion and tomatos.
Finishing Step - Drizzle tamarind sauce over the salad, and top with grilled shrimp