Process pecans in a food processor until the consistency of sand. Mix with melted butter, sugar, egg white, and salt. Using your hands, press equal portions of this mixture into eight muffin tins. Reserve in refrigeration.
Whisk egg yolks, sugar, cornstarch, vanilla, zest, and salt until smooth. Heat milk in a saucepan until a soft skin starts to form on the surface (do not boil). Add a small splash of milk to the egg mixture while continuously whisking (to prevent scrambled eggs). Add the remaining milk and combine well. Return all to the saucepan and heat until thickened (whisking continuously—approximately three minutes). When thick, chill and reserve.
Fill each of the nut-crusted muffin tins with equal portion of custard.
Put apple slices in a bowl with enough water to cover and the juice of one lemon. Heat in a microwave until tender (approximately two minutes). Drain and dry slices.
Arrange apple slices in an overlapping three-inch line. Gently roll from the left to the right, holding tightly to form a “rose.” Repeat seven more times so there are eight total apples. Place one rose into each of the custard-filled nut crusts.
Bake at 375 degrees F for 25 minutes or until crust starts browning, custard is firm, and apples are tender.
Optional: brush apple roses with warm jam.