Bring ketchup, 1 cup water, vinegar, brown sugar, onion powder, chili powder, tomato paste, molasses, and freshly ground pepper to a boil in a large saucepan over medium heat, stirring occasionally. Reduce heat to low; cover and cook, stirring occasionally, 25 minutes or until slightly thickened. Cool 10 minutes. Cover and chill until ready to serve. Store in refrigerator up to 1 week.