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1
Preheat the oven to 350u00b0. Put the onions in a small baking dish, root ends down, and rub with oil. Add 1/2 inch of water to the dish. Cover with foil and bake for about 1 1/2 hours, until tender. Let cool slightly.
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2
Meanwhile, heat a large skillet. Add the spinach in batches, tossing until wilted. Transfer to a colander and squeeze out the water. Coarsely chop the spinach.
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3
In the same skillet, cook the lamb over moderately high heat, breaking it up, until no pink remains, 3 minutes. Pour off all but 1 tablespoon of the fat and add the ancho chile powder and cinnamon. Cook over moderately high heat, stirring, for 1 minute. Stir in the spinach. Transfer the lamb filling to a large bowl. Stir in the bread crumbs, Gruyere, 1/4 cup of the beef broth and 1/2 cup of the crushed tomatoes.
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4
Cut 1/2 inch off the top and bottom of the baked onions. Separate the layers, trying not to break them. You will need 10 onion cups: some large, some medium and 2 small. Finely chop enough of the onion scraps to make 1/2 cup; fold into the lamb filling and season with salt and pepper.
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5
Stand the onion cups in a buttered medium baking dish. Season the insides with salt and fill with the lamb.
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6
In a large skillet, combine the cream with the remaining 3/4 cup of beef broth and 1/2 cup of tomatoes and bring to a boil. Pour the sauce over and around the onions.
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7
In a bowl, combine all of the ingredients. Mound the topping on the onions. Cover with foil and bake for 40 minutes, until hot. Uncover and increase the oven temperature to 425u00b0. Bake for 5 minutes, until the topping is crisp. Let rest for 5 minutes before serving.
