Preheat the oven to 375°F (190°C).
Season the salmon fillets with salt, pepper, and dried thyme. Place them on a baking sheet lined with parchment paper.
In a large skillet, heat the olive oil over medium heat. Add the diced eggplant, zucchini, bell peppers, onion, and garlic. Cook until the vegetables are tender, about 8-10 minutes. Season with salt, pepper, and dried oregano.
Add the diced tomatoes to the skillet and cook for an additional 2 minutes.
Spread the ratatouille mixture over the salmon fillets.
Bake in the preheated oven for 20-25 minutes, or until the salmon is cooked through.
Serve the baked salmon with ratatouille hot and enjoy!