Pour about 2 teaspoons oil from anchovy can into a skillet over medium heat; cook and stir onion in the hot anchovy oil until softened, about 5 minutes.
Add anchovy fillets; cook and stir until fish dissolves, about 5 minutes.
Stir tomato paste into onion-anchovy mixture; add juice from canned salmon, water, pine nuts, raisins, salt, and black pepper. Cook and stir mixture until flavors have blended, about 15 minutes.
Bring a large pot of lightly salted water to a boil. Cook spaghettini in the boiling water, stirring occasionally until cooked through but firm to the bite, about 12 minutes.
Drain.
Mix salmon and saffron into onion-anchovy mixture; cook until salmon is heated through, about 15 more minutes.
