Preheat oven to 350°F (180°C). Line a rimmed baking sheet with aluminum foil and place tomatoes and half of garlic head on it. Roast in oven until tomatoes are wrinkled and lightly charred in spots and garlic is soft, about 1 hour. Let cool.
Meanwhile, place dried peppers in a medium heatproof bowl and cover with boiling water. Place a weight or wet paper towel on top to help submerge peppers. Let stand until peppers are fully softened, 30 minutes to 1 hour. If peppers are very stubborn (as thick-skinned ñoras can be), you may need to tear a small hole in them to let water penetrate inside.
Drain peppers and discard stems and seeds. Using a paring knife , carefully scrape the flesh from the skins. Discard skins. Peel skins from tomatoes and roasted garlic.
Using a Mortar and Pestle
Add 3 cloves roasted garlic and 1 or 2 cloves peeled raw garlic to mortar. (Feel free to make this recipe more or less garlicky, according to your own tastes, by adding or subtracting roasted or raw garlic.) Smash garlic to a paste with pestle.
Add bread and moisten with vinegar. Smash to a paste. Add nuts and smash as finely as you can. The mixture should have the consistency of a rough paste when you're done.
Smash in scraped pepper flesh, followed by peeled roasted tomatoes. Mix in olive oil until thoroughly combined. Season with salt. Add more oil, 1 tablespoon (15ml) at a time, if a thinner, richer sauce is desired. Add more vinegar to taste as well.
Using Countertop or Immersion Blender
Add 3 cloves roasted garlic and 2 cloves peeled raw garlic to jar of blender, or blending container if using an immersion blender. (You can use more or less roasted and raw garlic, as desired, according to your own tastes.) Add nuts. Blend until finely processed, scraping down sides as necessary.
Blend in peeled roasted tomatoes and scraped pepper flesh. Add bread, olive oil, and vinegar, and blend until smooth. (How smooth to make it is up to you; some texture is okay.) Season with salt and add more oil and vinegar to taste, if desired.
Using Food Processer
In the bowl of a food processor, combine 3 cloves roasted garlic and 2 cloves peeled raw garlic (use more or less roasted and raw garlic, as desired, according to your own tastes), along with bread and nuts. Process, scraping down sides as necessary, until finely chopped.
Add peeled roasted tomatoes and scraped pepper flesh and process until a thick, rough paste forms. Process in olive oil and vinegar, then season with salt. Add more vinegar and olive oil, as desired, to adjust taste and texture.
Notes
Using three tomatoes instead of two will make a thinner, milder sauce.
Ñora peppers, with their earthy bitterness and molasses-like depth, are more traditional in this sauce. If you can't find them, ancho chile peppers are a good substitute.
Different nuts will give the sauce different flavors. Almonds and hazelnuts are most traditional, but you can also try adding pine nuts or walnuts. Experiment to see what you like most.
