In a bowl combine rhubarb, sugar, vanilla, salt and zest. Blend well and transfer to a 9 inch casserole dish or roasting pan.
Remove from oven and stir in lemon juice. Let it cool.
Any leftover shortcake stores very well in the freezer when in a sealed plastic bag.
The rhubarb and whipped cream will last a week or more in the refrigerator. You can also freeze them for longer storage.
Of course, this shortbread is perfect with your favorite strawberries from any strawberry shortcake recipe.
*For an egg-free version, use 3 Tbsp aquafaba to replace one egg.