1. Make the caponata: Heat 1 tablespoon of olive oil in a pan over medium heat. Add the onion and eggplant. Cook for about 8 to 10 minutes until softened.

2. Simmer: Add the garlic, diced tomatoes, capers, and olives to the pan. Reduce heat to low and let it simmer for 10 to 12 minutes until the tomatoes break down and the mixture thickens. Stir in the red wine vinegar, season with a pinch of salt and pepper, and remove from heat.

3. Grill the fish: Preheat your grill or heavy skillet to medium-high heat. Pat the halibut fillets dry with a paper towel, brush with the remaining olive oil, and season lightly with salt and pepper.

4. Cook: Grill the halibut for 3 to 4 minutes per side, depending on thickness, until the fish flakes easily with a fork.

5. Serve: Spoon the warm caponata onto plates, place the grilled halibut on top, and garnish with fresh herbs.