In a large bowl, stir pimentos, mayonnaise, cayenne, salt, pepper, garlic, and onion powder until combined.
4 ounce jar pimentos, drained, 3/4 cup mayonnaise, 1/8 teaspoon cayenne, 1/2 teaspoon salt, 1/4 teaspoon fresh ground black pepper, 1/2 teaspoon garlic powder, 1/2 teaspoon onion powder