01 - Preheat the oven to 400°F. Lightly grease a large baking dish or sheet pan with cooking spray or a small amount of olive oil.
02 - In a large mixing bowl, combine the halved potatoes and red onion wedges. Drizzle with olive oil, then add lemon zest, lemon juice, minced garlic, dried oregano, black pepper, chili flakes, and salt. Toss thoroughly until all vegetables are evenly coated.
03 - Spread the seasoned potato and onion mixture evenly across the prepared baking dish in a single layer for optimal browning.
04 - Distribute the feta cheese cubes evenly over the top of the potato mixture, allowing some pieces to rest partially on vegetables for better browning.
05 - Bake for 35 to 40 minutes, stirring the potatoes once halfway through cooking. The dish is ready when potatoes are tender when pierced with a fork, edges are golden brown, and feta has developed light golden spots.
06 - Remove from oven and immediately sprinkle with additional fresh chopped parsley. Serve warm while the feta is still slightly melted and creamy.