Grease 6-inch round cake pan and line bottom with parchment paper.
Whisk together flour, baking powder and salt; set aside.
In separate bowl, stir together brown sugar, melted butter, egg and vanilla. Then stir in the flour mixture just until combined. Fold in 1/2 of the pecans, then scrape the batter into the prepared cake pan and smooth the top.
If using an Instant Pot Duo Crisp ensure the inner pot is dry. Place trivet in to the inner pot with the cake pan uncovered on top. Using the Air Fryer Lid select Bake at 176°C for 25 minutes. When the time is up, remove the Air Fryer lid and top the blondies with marshmallows, chocolate, digestives, remaining pecans and sea salt, then drizzle with dulce de leche. Put the Air Fryer lid bake on a select Grill for 3 to 5 minutes or until chocolate is melted. Lift out carefully from inner pot; let cool completely.
If using a Vortex Air Fryer, select Bake and set the time for 25 minutes and temperature to 176°C and press Start. Place the cake pan in the frying basket when prompted to Add Food.
When the time is up, open the frying drawer and top the blondies with marshmallows, chocolate, digestives, remaining pecans and sea salt over top. Drizzle with dulce de leche.
Select Bake again and set the time for 5 minutes, and cook until chocolate is melted. Lift out carefully from inner pot; let cool completely.