Meanwhile, melt the butter in a medium saucepan. Add the onion and garlic and cook over low heat until softened. Add the paprika, ancho powder and crushed red pepper; cook, stirring, for 1 minute. Add 1 cup of water, the brown sugar and vinegar and bring to a simmer. Stir in the tomato paste and molasses and simmer over low heat, stirring occasionally, until the sauce is thickened, about 10 minutes. Season with salt and let cool.