Preheat oven to 400 degrees F (200 degrees C). Grease a 9x13-inch baking dish with about 1 teaspoon olive oil.
Place trout in the prepared baking dish and coat with remaining olive oil. Season the inside and outside of fish with salt, thyme, and salt. Stuff fish with onion slices; grind pepper over the top. Place basil inside of fish.
Bake in the preheated oven for 10 minutes; Continue baking until fish flake easily with a fork, about 10 minutes more.
Serve with side of your choice and veggies of your choice.
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