Heat 1 tablespoon oil in a large skillet over medium-high heat. Season the lamb with paprika, cinnamon, ½ teaspoon salt, and ¼ teaspoon pepper.
Cook the lamb, 4 to 6 minutes per side for medium-rare. Let rest at least 5 minutes before slicing.
Meanwhile, heat the remaining tablespoon of oil in a medium saucepan over medium-high heat.
Add the onion and cook, stirring occasionally, until softened, 3 to 4 minutes.
Stir in the couscous, apricots, saffron (if desired), 1 teaspoon salt, ¼ teaspoon pepper, and 2 cups water. Bring to a boil.
Reduce heat and gently simmer, covered, until couscous is tender and water is absorbed, 8 to 10 minutes. Fold in spinach and serve with lamb.