In a mixing bowl, combine cheeses, cream cheese, diced pimentos, mayonnaise, onion powder, garlic powder, and cayenne powder. Stir to mix well. Add salt and pepper to taste, as desired.
Spread 6 slices white bread with pimento cheese. Top with remaining 6 slices white bread. Cut each sandwich on the diagonal and serve.
Store leftover Masters pimento cheese in the refrigerator. Also enjoy leftover pimento cheese with chips, pita chips, crackers, veggie slices, etc.