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1
Prepare the romesco sauce: If using a dried pepper, remove the stem and seeds from the pepper and soak in warm water for 1 hour, or until softened.
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2
Scrape off the flesh and discard skin.
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3
If using a roasted pepper, remove the charred skin, stem, and seeds, and chop.
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4
Set aside.
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5
In a food processor, finely chop the bread and almonds.
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6
Add the salt, pepper, garlic, tomato and reserved flesh of the pepper.
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7
Process to a smooth paste.
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8
With the motor running, add the olive oil in a thin stream, until mixture is the consistency of a thick, creamy sauce.
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9
Add the warm water as needed to help thin the sauce if necessary.
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10
Adjust the seasonings, transfer to a bowl and set aside at room temperature or chill until ready to serve.
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11
Preheat a grill or broiler, and preheat an oven to 400 degrees F. Trim the roots off the onions and spread them over the grill.
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12
Grill the onions until charred all over but not dried out, turning frequently.
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13
Transfer the onions to a large roasting pan, cover tightly and roast in the oven for 20 to 25 minutes.
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14
Serve the onions steaming hot, strip back the charred outer skin, dip the onions in the romesco sauce, eat the white bottoms and discard the top.
