Prebake tart shell and brush warm shell with apricot preserves. (SQ note - Baking time was not included in this recipe but listening to reviewers leads me to think that 15 minutes at 350F should be about right.).
Peel, core and slice apples.
Sprinkle with lemon juice.
Arrange apple slices in tart shell.
Scatter walnuts on top of fruit.
Combine sugar, flour and cinnamon in small bowl.
Add butter and work with fingers to form a crumb topping.
Sprinkle over tart.
Bake at 400 for about 40 minutes or until top is golden brown.