– 3 eggs (medium), hard-boiled – 3 tablespoons mayonnaise – 1 red onion (small), minced, divided – 1 bell pepper minced – 1 teaspoon salt (or more, to taste), divided – 1 avocado ripe – 2 plum tomatoes minced – ½ teaspoon vinegar – 9 slices white sandwich bread – 1 dozen pitted green olives (optional)