Preheat the oven to 400°F (204°C).
In a small pot over medium heat, combine the stock, apricots, and lemon zest. Gently simmer until the apricots are plump and the liquid is reduced to 1/2 cup, roughly 10 minutes.
Without peeling the onions, cut about 1 inch off the tops and just enough off the bottoms that each onion stands upright. Reserve the onion tops and discard the bottoms. Remove all but the outer two layers of each onion by scooping out the centers with a spoon or melon baller, reserving the insides. Set the onion shells in a baking dish along with the tops. Finely chop the insides.
Melt 3 tablespoons of the butter in a skillet over medium-low heat. Stir in almost all of the chopped onions, reserving some for another use, and cook until softened, 10 to 12 minutes. Add the lamb, cinnamon, and cumin and season with salt and pepper. Raise the heat to medium-high and cook, continually stirring with a wooden spoon, until the lamb is crumbly, 7 to 8 minutes. Don't drain the rendered fat; it's needed to keep the onions moist and to impart a luscious unctuousness to the overall dish.
Remove the pan from the heat. Stir in the apricot mixture and its liquid, hot sauce to taste, and the parsley and mint. Let cool slightly. (The lamb filling can easily be prepared a day in advance, covered, and refrigerated.)
Spoon some of the lamb mixture into each of the hollowed-out onions, pressing down with your hands and mounding it over the onions. Sprinkle the bread crumbs over the onions and dot with the remaining 2 tablespoons butter.
Cover the pan tightly with aluminum foil and bake until tender, 30 to 45 minutes, depending on the size. Remove the foil and continue to bake until the bread crumbs are brown, about 10 minutes more. Serve immediately.