Rip the bread into large pieces and put them into a bowl. Add water to cover, then pull out the bread quickly and squeeze out the excess water, leaving squishy soaked bread.
Place the bread in a food processor or blender, and add the pimentos, lemon juice, garlic, paprika, cayenne and salt. Process until well blended. Add the olive oil in a very thin steady stream, using the insert made for this purpose or just doing it by hand. As the oil gets incorporated the mixture should emulsify (thicken).