Squeeze lemon juice over the avocado halves to prevent browning. Slightly score inside of each avocado halve; sprinkle with salt and pepper.
In a small bowl, combine sour cream and mayonnaise; divide mixture between the four (4) avocado half cavities. Sprinkle each with some diced eggs and diced onions.
Place each prepared avocado half on individual serving plates and serve.
Linda's Favorite Recipe using Avocado Halves: https://whatscookingamerica.net/appetizers/avohalfshell.htm