Zesty French Dressing

1 small onion, chopped
2/3 cup vegetable oil
1/2 cup sugar
1/3 cup vinegar
2 tablespoons ketchup
1-1/2 teaspoon Worcestershire sauce
1-1/2 teaspoons salt
1 teaspoon prepared mustard
1 teaspoon paprika
1/2 teaspoon garlic powder
1/2 teaspoon celery seed

In a blender or food processor, process all ingredients until smooth and thickened. Cover and refrigerate for at least 1 hour. Shake well before serving. Makes about 1-1/2 cups.