Grilled Fish Tacos

From Bon Appétit, May 2008

* 2 cups chopped white onion, divided
* 3/4 cup chopped fresh cilantro, divided
* 1/4 cup olive oil
* 5 tablespoons fresh lime juice, divided
* 3 tablespoons fresh orange juice
* 2 garlic cloves, minced
* 1 teaspoon dried oregano (preferably Mexican)
* 1 pound tilapia, striped bass, or sturgeon fillets
* Coarse kosher salt
* 1 cup mayonnaise
* 1 tablespoon milk
* Corn tortillas
* 2 avocados, peeled, pitted, sliced
* 1/2 small head of cabbage, cored, thinly sliced
* Salsa Verde
* Lime wedges

Stir 1 cup onion, 1/4 cup cilantro, oil, 3 tablespoons lime juice, orange juice, garlic, and oregano in medium bowl. Sprinkle fish with coarse salt and pepper. Spread half of onion mixture over bottom of 11x7x2-inch glass baking dish. Arrange fish atop onion mixture. Spoon remaining onion mixture over fish. Cover and chill 30 minutes. Turn fish; cover and chill 30 minutes longer. Whisk mayonnaise, milk, and remaining 2 tablespoons lime juice in small bowl.

Brush grill grate with oil; prepare barbecue (medium-high heat). Grill fish with some marinade still clinging until just opaque in center, 3 to 5 minutes per side. Grill tortillas until slightly charred, about 10 seconds per side.

Coarsely chop fish; place on platter. Serve with lime mayonnaise, tortillas, remaining 1 cup chopped onion, remaining 1/2 cup cilantro, avocados, cabbage, Salsa Verde, and lime wedges.