This recipe uses up more of that cabbage hiding in the back of your crisper and some of those onions we are receiving this week.
- 1 medium red onion
- 1/2 cup cider vinegar
- 1/4 cup sugar
- 7 tablespoons fresh lime juice, divided
- 1/4 cup chopped cilantro
- 1 tablespoon olive oil
- 1 1/4 pound (1-inch-thick) skinless mahimahi fillet or tuna steak, cut into 12 pieces
- 2/3 cup mayonnaise
- 2/3 cup crema or sour cream
- 12 (6-inch) corn tortillas
- 6 to 8 radishes
- 1 to 2 (6- to 8-ounce) firm-ripe avocados
- 4 cups thinly sliced green cabbage (1/2 small head)
- Equipment: an adjustable-blade slicer; 12 (6- to 8-inch) wooden skewers, soaked in water 30 minutes
- Accompaniment: lime wedges
Very thinly slice onion crosswise into rings with slicer. Set slicer aside. Heat vinegar, sugar, and 1/2 teaspoon salt in a small heavy nonreactive saucepan until sugar has dissolved. Remove from heat and stir in onion, then let stand until ready to use (about 25 minutes).
Meanwhile, stir 1/4 cup lime juice together with cilantro, oil, and 1/2 teaspoon salt. Add fish and toss to coat, then marinate at room temperature 15 minutes.
Whisk together mayonnaise, crema, 1/2 teaspoon salt, and remaining 3 tablespoons lime juice to make sauce.
Preheat a gas grill with burners on high, covered, 10 minutes, then reduce heat to medium-high.
Thread each piece of fish onto a skewer (discard marinade). Wrap exposed part of each skewer in heavy-duty foil to protect it from charring.
Wrap tortillas in 2 foil packages and warm on grill, turning once, about 3 minutes total.
Oil grill rack, then grill fish, covered, turning once, until opaque and just cooked through (for mahimahi), about 6 minutes total; or until just pink in center (for tuna), about 4 minutes.
Very thinly slice radishes with slicer. Halve, pit, and peel avocados, then cut into 1/2-inch-thick slices. Drain onions.
Serve fish with tortillas, crema sauce, onions, and remaining toppings.
Cooks' note If you aren't able to grill outdoors, cook fish in a lightly oiled large (2-burner) ridged grill pan. Warm tortillas in foil packages in grill pan 2 to 3 minutes or in a 300°F oven 10 minutes.