In a small bowl, whisk together sour cream, mayonnaise, lime zest, juice and salt. Cover and refrigerate until ready to use.
Mango Feta Salsa
In a bowl, stir together mango, shallot, pepper, cilantro, lime juice, feta and salt; set aside.
Preheat grill to medium high heat and grease grill.
In a small bowl, stir together chili powder, salt, garlic powder, thyme leaves, lime zest and cayenne. Brush fillets with butter and sprinkle all over with spice mixture.
Place on prepared grill and grill for about 10 minutes or until fish flakes when tested with fork.
Remove to plate and carefully break halibut into 12 pieces. Divide among tortillas and spoon salsa over top.
Drizzle with crema to serve. Garnish with cilantro leaves if desired.
Top 5 Nutrients: Selenium 73%DV, Niacin 69 %DV, Vitamin B12 56%DV, Vitamin C 40%DV, Vitamin B6 31%DV.