The one on the scallops was pretty much a couli. It was just roasted red bell, S and P, a bit of cayenne, and red wine vinegar. We thought it had too much vinegar, followed recipe, so added a bit of honey.
The red bell sauce I use for shrimp, crab or lobster ravioli is made from roasted red bells, diced onion and minced garlic that have been sauteed in butter and olive oil, cooled and zapped in food processor. That is then mixed with whatever is left from a plain bechemel used to bind the chopped seafood together, plus a splash of a light white wine, and seafood stock to make a smooth creamy sauce. If I don't have enough bechemel, I'll use heavy cream.
Red bell pairs exceedingly well with the above seafood.