Use a small knife to slice enough off the top and bottom of the orange so that the tips of the segments are exposed, then cut off the skin and all the pith using downward cutting strokes, removing the white pith. Cut between the thin membranes to release the segments and halve the segments crosswise. Set aside.

Heat the oil over medium heat in a large saucepan with a lid. Add the garlic and cook one minute. Add the spinach and toss to coat with the oil and garlic. Cover and cook until the spinach is just wilted but still bright green, about two minutes. Remove from heat, drain off any liquid and season with salt and pepper. Stir in the orange segments and garnish with pomegranate seeds.