Heat 3 tablespoons of the olive oil a Dutch oven or deep rondeau pan over medium heat. Add the onions, peppers, garlic, jalapeno and a pinch of salt and cook until the vegetables are tender and slightly caramelized, 3 to 5 minutes. Stir in the cumin, paprika and cayenne and toast for a minute before stirring in the tomatoes. Season with salt and pepper and simmer for 15 minutes, until all of the flavors come together. Remove from the heat and stir in the sherry vinegar to taste.
Season the fish pieces on both sides and nestle into the sauce, leaving spacing in between. Roast, uncovered for 15 to 20 minutes, until the fish is cooked through.
In the meantime, remove the rind and segment the orange, reserving any juice. To a mixing bowl, add the arugula, olives and orange segments. Add in some of the orange juice and drizzle with the remaining 2 tablespoons of olive oil. Season with salt and toss to coat the arugula.
Place a piece of halibut onto a plate with a scoop of the tomato mixture. Top with some arugula salad and serve.