Heat oil in a medium skillet over medium heat. Add onion and garlic, and cook until lightly colored, about 3 minutes. Add tomato, jalapeno and white wine. Cook until wine is reduced by 2/3, about 5 to 7 minutes. While sauce is reducing, heat butter in a separate skillet over medium heat. Season fish with kosher salt. When butter is melted, add halibut to the pan. Cook for 2 minutes, flip over and then transfer pan to preheated oven and bake until cooked through, about 10 minutes. Remove sauce from heat when reduced and stir in olives and olive juice.
To serve, divide sauce equally among 4 dinner plates. Place halibut (first caramelized side up) in the center of each plate on top of the sauce. Place avocado slices on top of fish, sprinkle with lime juice and cilantro, as garnish.