With a small melon bailer, scoop out the avocado flesh to within 1/8 inch of the skin.
Reserve the avocado shells.
Place the avocado balls in a medium sized mixing bowl and sprinkle over the tablespoon of lemon juice.
Set aside.
Scoop out the melon flesh in the same way and add the melon balls to the avocado balls.
Place the bowl in the refrigerator to chill while you make the dressing.
In a small mixing bowl, beat the oil, salt and pepper together with a fork.
Gradually add the lemon juice.
Remove the melon and avocado from the refrigerator and pour over the dressing.
With a wooden spoon carefully toss the ingredients together until the balls are well coated.