Halibut Fish Tacos with Guacamole Sauce

Name: Halibut Fish Tacos with Guacamole Sauce
Ingredients: 4 pieces fresh halibut, steak or filets, 6 to 8 ounces each; Extra-virgin olive oil, for drizzling; Salt and pepper; 1 lime, juiced; 3 small to medium ripe Haas avocados, pitted and scooped from skins with a large spoon; 1 lemon, juiced; 1/2 teaspoon cayenne pepper, eyeball it; 1 cup plain yogurt; 1 teaspoon coarse salt, eyeball it; 2 plum tomatoes, seeded and chopped; 2 scallions, thinly sliced on an angle; 1 heart Romaine lettuce; 12 soft (6-inch) flour tortillas