Heat 1/4 cup of olive oil in a large, heavy skillet over medium-high heat. Add the halibut steaks two at a time and cook until crispy and golden (about 2-3 minutes). Flip the steaks and cook the other side similarly. Remove the finished halibut from the pan and repeat with the remaining steaks. Set all of the fish aside in a deep dish, ideally just large enough to hold everything in a single layer.

Allow the oil to return to heat back up for about 30 seconds, then add the onions, garlic, and jalapeños. Saute for 2-3 minutes, then add the oregano, cumin, bay leaves, and peppercorns. Cook for an additional 3 minutes. Add the vinegar and bring the mixture to a simmer. Simmer for 5 minutes.

Transfer the cooked vegetables, spices, and vinegar to the dish with the halibut. Pour the mixture over the fish, then add the remaining olive oil. IF EATING THAT DAY: Set the fish aside and marinade at room temperature for 5 hours. IF EATING ANOTHER DAY: Set the fish aside at room temperature for 2-3 hours, then refrigerate for up to 1 week. Return the fish to room temperature or (slightly warmed) before serving.

The fish can be served as is with some of the marinated vegetables, roasted vegetables, rice, or any other side you might enjoy. It can also be cut into pieces and served in tacos along with the marinade, roasted tomatoes, cilantro, etc.