Heat the oven to 375°F. Put the tomatoes and one half of the garlic head in a baking pan. Drizzle about 1 Tbs. of the olive oil into the cored tomato wells and on top of the garlic half. Roast until the tomatoes and garlic are well caramelized but not burnt, about 90 minutes. From the remaining half head of garlic, coarsely chop 1 Tbs. garlic and put it in a food processor.
Slow oven roasting brings out the sugars in tomatoes and garlic. Get them caramelized but not burnt.
While the tomatoes roast, heat about 1 Tbs. of the olive oil in a small sauté pan over medium heat. Toast the almonds and hazelnuts in the pan, shaking the pan or stirring so they don't burn, until golden brown, 5 to 6 minutes. Cool the nuts on a paper towel and then put them in the food processor.
If using a dried chile, sear it in the same small pan over medium-high heat (keep it flat with a spatula or a fork) until a smoke wisp appears, about 10 seconds per side. Soak it in 1 cup hot tap water until soft, about 15 minutes. Drain and put the chile in the food processor.
Start with the toasted nuts, chile, and tomatoes to get the purée underway.
Bill Devin pours in olive oil slowly to create an emulsified sauce, adds vinegar, and then tastes the romesco before making adjustments.
When the tomatoes and garlic are caramelized, let them cool. Pinch off the tomato skins (discard them) and squeeze out the garlic pulp. Put the tomatoes and garlic pulp in the processor. Add the salt and start the processor, pouring in the remaining 1/3 cup olive oil in a slow, steady stream, as if making mayonnaise. Add the vinegar, pulse to incorporate, and taste; the sauce should have some zing, so add more if needed. Add salt to taste. Process the romesco until it comes together as a sauce but not so much as to lose its coarse, nutty texture. The sauce should be thick and creamy. If it seems too thick, add 1 or 2 Tbs. red wine. If it's too thin, add bread, pulsing a few more times.