Grated apple adds a touch of fall to this Canadian classic.
MAKE AHEAD
Prepare butter-tart filling, omitting grated apple. Cover filling and refrigerate overnight or up to 2 days. (Do not freeze.) Immediately prior to baking, bring filling to room temperature. Then peel and grate apple, dividing grated apple between tart shells. Whisk filling and pour into shells. Bake as above.