The trick to getting the apple pieces to soften a bit to be pliable to fill your tart is to mix them in the low carb sweeteners, the butter, and lemon juice. When it sits for 15-20 minutes, the apples naturally soften enough to bend. You will need to also cut them into crescent moons around 1/8th of an inch thick as well.
If you have the time, it’s well worth making a French apple tart, a classic shop-window patisserie. For the pastry, rub the butter into the flour, sugar and a pinch of salt in a bowl until crumbly. Mix in the egg until it forms a dough, then form into a puck shape. Cover and chill for at least 30 mins. Will keep chilled for two days.
Directions. Peel the apples and cut them in half through the stem. Remove the stems and cores with a sharp knife and a melon baller. Slice the apples crosswise in 1/4-inch thick slices. Place overlapping slices of apples diagonally down the middle of the tart and continue making diagonal rows on both sides of the first row until...
Whisk until smooth and brush or spoon evenly over the top of the apples. Bake the tart for 30 minutes at 375 degrees (F). Remove the tart and gently press the apples down flat with the back of a spoon or spatula. Reduce the heat to 350 degrees (F) and bake the tart for another 20 minutes.