Preheat the oven to 350 F. Lightly spray a 10" to 12" cake pan or cast iron skillet with non stick spray. If using a Springform pan, line it with foil so the buttery topping doesn't leak out!
Combine the melted butter, brown sugar, corn syrup, and salt. Whisk well to blend. Add the pecans.
⅓ cup brown sugar, 2 tablespoon corn syrup, ⅓ cup butter, ¼ teaspoon salt, 1 cup pecans
The butter and sugar mixture will thicken up as the butter cools. Spread mixture into the bottom of the prepared cake pan or skillet. Set aside.
Cream the sugar and butter in a large mixing bowl until fluffy. Add the eggs and vanilla and mix well.
1½ cup sugar, ¾ cup butter, 2 eggs, 1 teaspoon vanilla
In a separate bowl, whisk the flour baking powder, salt, and nutmeg. Add to the wet ingredients. Combine with an electric mixer.
1½ cups Flour, 2 teaspoon baking powder, ¼ teaspoon salt, ¼ teaspoon nutmeg
Spread the blondie batter on top of the pecan tarte tatin topping in the cake pan. Using a spatula, spread the blondie batter out evenly in the cake pan.
Set the cake pan or skillet in the preheated oven and bake for 35 to 40 minutes, or until the blondie top is golden brown. Remove cake from oven and cool on a cooling rack for 5 minutes.
Lay a large cake plate upside down over the cake pan. Invert the cake pan and cake plate so that the cake tips out upside down onto the cake plate. Let cool and serve with whip cream.