Cook 1 sliced red onion in 1/4 cup olive oil until golden. Add 2 cups sliced mushrooms and cook until brown; season with salt. Off the heat, stir in 1/2 cup torn parsley, 10 ounces spinach and the juice of 1 lemon. Season with salt and pepper. Sprinkle with 1/2 cup feta.
Photograph by Antonis Achilleos