For perfect apple cubes: Stand the apple on your cutting board and cut down into four slabs; discard the core. Lay slabs, cut sides down, and cut into 1/2-inch slices, then crosswise into 1/2-inch cubes.
Combine mayonnaise and lemon juice in a medium bowl. Add apples, grapes, and cranberries; mix well.
Add the walnuts and celery, and mix well. Serve it on a bed of 2 lettuce leaves. The salad can be refrigerated up to 2 hours before serving.
This turned out very well. I used vegan mayo, very good.
A very nice touch to a formal dinner.