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1
Preheat the oven to 325.
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2
Peel off the outer layers of the onions until each one is about 3 inches in diameter.
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3
Trim the root ends so the onions stand upright.
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4
Arrange the onions on a large rimmed baking sheet and cover with foil.
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5
Bake for about 4 hours, until they are partially softened.
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6
Remove the foil and bake the onions in the upper third of the oven for 2 hours longer, rotating them occasionally, until they are very tender and richly browned outside.
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7
If the onions start to pop out of their skins, push them back in.
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8
Meanwhile, spread the chopped olives on a microwave-safe plate.
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9
Microwave at high power for 12 minutes until the olives are dehydrated but still plump; transfer to a food processor and pulse until finely chopped.
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10
Transfer the olives to a medium bowl and wipe out the food processor.
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11
Pulse the almonds in the food processor until finely ground; transfer to a rimmed baking sheet and toss with the demerara sugar.
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12
Bake in the same oven as the onions for about 6 minutes, stirring a few times, until golden and toasted.
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13
Let cool.
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14
Add the almonds to the olives and toss well.
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15
In a saucepan, bring the demiglace to a boil.
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16
Transfer to a blender.
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17
Add the oil and vinegar and blend well.
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18
Season with salt.
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19
Using a serrated knife, cut off the top fourth of each onion.
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20
Transfer the onions to plates.
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21
Spoon the vinaigrette on top and garnish with the almond-olive mixture.
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22
Serve right away.
