In large nonreactive saucepan, melt butter. Add onion, garlic, and salt. Cook over low heat until onion is tender. Add crushed red pepper, paprika, chili powder, and black pepper; cook and stir for 1 minute.
Add water, vinegar, brown sugar, and Worcestershire sauce; bring to a simmer. Stir in molasses. Whisk in tomato paste until smooth. Bring to a simmer over low heat. Cook, uncovered, for 10 to 15 minutes or until sauce is thickened, stirring occasionally. Taste for seasoning, adding additional salt if needed. Store in the refrigerator; reheat to serve.