Preheat oven to 425 degrees. Line a 9 by 12-inch baking dish with parchment paper.

Rinse cod fillets under cold running water and pat dry with paper towels. Place cod fillet(s) in prepared dish and brush with lemon olive oil. In a small bowl, combine feta cheese, lemon zest and dill; sprinkle on top of the cod.

Roast in the preheated oven, uncovered, for 8 to 10 minutes per 1-inch of thickness (at its thickest point), until opaque and just cooked through.

Switch the heat to broil and broil for 2 minutes to melt and lightly brown some of the cheese.

In a large sauté pan, heat 2 teaspoons extra virgin olive oil over medium heat. Add green onions, garlic and around half of the spinach. Cook until wilted, then add remaining spinach and continue to cook.

Remove from heat and stir in bread crumbs and red pepper flakes (if using); season with salt and pepper.

Divide cooked spinach among four dinner plates. Top with cod fillet. Serve immediately, with lemon wedges on the side.