• 1/4 cup low-fat sour cream
• 3 1/2 tablespoons fresh lime juice, divided
• 2 small plum tomatoes, seeded and diced
• 2 1/2 tablespoons olive oil, divided
• 2 tablespoons chopped fresh cilantro
• 1 teaspoon minced seeded jalapeño pepper
• 3/4 teaspoon salt, divided
• 1/4 teaspoon freshly ground black pepper, divided
• 1 1/2 cups thinly sliced red onion
• 8 (6-inch) tortillas
• 1 pound grouper or other firm white fish fillets
• 1/2 teaspoon chili powder
• 1/4 teaspoon cumin
• Non-stick cooking spray
• 2 cups shredded red cabbage or shredded romaine

Marinate Fish: 

In a large zip-top plastic bag, combine the fish fillets, 1 1/2 teaspoons of olive oil, 1 1/2 teaspoons of lime juice, chili powder, cumin, 1/4 teaspoon of salt, and 1/8 teaspoon of black pepper. Gently toss to coat the fillets evenly.

Prepare the Sour Cream Sauce:

In a small bowl, combine the low-fat sour cream with 2 tablespoons of lime juice. Cover and refrigerate.

Make Salsa:

In a bowl, diced tomato, red onions, 1 tablespoon lime juice, 1 tablespoon olive oil, chopped cilantro, minced jalapeño, 1/4 teaspoon salt, and 1/8 teaspoon black pepper. Toss gently, then cover and chill.

Prepare Tortillas:

Heat the tostada shells according to package directions and keep them warm.

Grill the Fish:

Preheat the grill. In a large zip-top plastic bag, combine the fish fillets, 1 1/2 teaspoons olive oil, 1 1/2 teaspoons lime juice, chili powder, cumin, 1/4 teaspoon salt, and 1/8 teaspoon black pepper. Toss gently to coat.

Place the fish on a grill rack coated with non-stick cooking spray and grill for 6 to 7 minutes on each side, or until the fish flakes easily with a fork. Flake the fish into bite-sized pieces.

Assemble the Tostadas:

Divide the flaked fish evenly over the tortillas.

Top each tortilla with desired amount of red cabbage or lettuce.

Top the fish with the salsa and drizzle with the sour cream mixture.