Mix the cream cheese, mayonnaise, onion, seasonings and pimentos together.
Add the cheddar cheese and mix well.
Cover and chill overnight or at least 4 hours before serving. Serve with crackers or fresh vegetables.
The calories shown are based on the recipe being divided into 16 servings, with 1 serving 1/16 of the dip. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate.