Preheat your oven to 400°F (200°C).

Rinse the halibut fillets under cold water and pat them dry with paper towels. Season both sides with salt and pepper.

In a large oven-safe skillet, heat the olive oil over medium-high heat. Once hot, add the halibut fillets and sear for about 2-3 minutes on each side until golden brown. Remove the fillets from the skillet and set aside.

In the same skillet, add the chopped red onion and garlic. Sauté for about 2 minutes until the onion is translucent and the garlic is fragrant.

Stir in the halved cherry tomatoes, sliced olives, dried oregano, and dried basil. Cook for an additional 3-4 minutes until the tomatoes start to soften.

Add the lemon juice and fresh parsley to the skillet, stirring to combine.

Return the halibut fillets to the skillet, spooning some of the Mediterranean sauce over the top.

Transfer the skillet to the preheated oven and bake for 10-12 minutes, or until the halibut is cooked through and flakes easily with a fork.

Remove the skillet from the oven and let it rest for a minute. Serve the halibut topped with the Mediterranean sauce and garnish with crumbled feta cheese.