Peel, de-core and slice the apples into thin pieces (approx 4-5mm).
In a large frying pan, heat the butter on a medium setting until melted.
Add the apples and brown sugar and fry for about 5 minutes, stirring frequently, until slightly softened and starting to brown.
Add the dulce de leche and lower the heat. Cook for another 5 minutes, stirring frequently. Remove from the heat and allow to cool for about 10 minutes or until comfortable to handle.
While the apples are cooling, preheat the oven to 180°C/160°C fan.
Arrange the dulce de leche covered apples in your tart crust, starting on the outer edge and working your way towards the centre. Or just spoon them in and spread them out in an even layer.
Bake for 30-35 minutes. The apples should be soft and caramelised.
Serve with more warm dulce de leche drizzled on top, or add cream, ice cream or custard!