Preheat the oven to 400°F (200°C).

Heat 2 tablespoons olive oil in an oven-safe nonstick skillet over medium heat. Add onions and cook until translucent, stirring frequently, for 3 to 4 minutes. Stir in garlic and cook for another 30 seconds.

Add cherry tomatoes and wine, then season with salt and pepper. Stir in 1 teaspoon of Italian seasoning and red pepper flakes. Cook for about 1 minute, remove from heat, and stir in olives, spinach, and cream.

Nestle the fish fillets into the vegetable mixture, season with salt and pepper, and drizzle the remaining olive oil over the dish. Sprinkle with the remaining 1/2 teaspoon of Italian seasoning.

Bake in the preheated oven until the fish is cooked through and flakes easily with a fork (20 to 25 minutes). An instant-read thermometer should register 145°F (63°C) at the center.