From the half box of the cake mix, take out ½ cup and set aside in a bowl for the topping, for later.
With the remaining cake mix, add a ¼ cup of melted butter, and ½ an egg (see notes). Mix together until combined.
Lightly spray the bottom of a 7-inch springform pan (or a different dish that will fit in your air fryer. A cake barrel or cake pan also works).
Spread the batter in the bottom of the pan. Cook in the air fryer for 320°F/160°C for 10 minutes.
In a bowl, mix together the pumpkin puree, ⅓ cup milk, and 1 egg.
In a separate bowl, mix together the ½ cup of cake mix, with 2 tablespoons of sugar, and 1/2 teaspoon of cinnamon. Then add in the butter and mix until crumbly with a fork.
Carefully remove the cake from the air fryer basket.
Add the pumpkin puree layer to the cake, then the crumble topping mixture.
To avoid the crumble mixture from blowing around in the air fryer, lightly spray the top of the cake with oil or cover with foil and take off during the last couple of minutes.
Cook in the air fryer at 320°F/160°C for another 10-15 minutes, or until the top is golden brown and the inside is cooked through.
Once cooled, remove from the springform pan and enjoy with whipped cream.
Notes
To get half an egg, whisk the egg in a small bowl and measure it on a scale. Take out half and put it in another bowl. For me, 1 egg weighed 55 grams. So I only used about 27 grams of egg for this recipe. Oven Instructions:This recipe works great in the oven as well. Just double the called for ingredients. Be sure to set aside 1 cup of cake mix for the crumble topping. Mix ingredients together as directed. Press the first layer into a lightly oiled 9x13 baking pan. Place the pumpkin layer next, and then finally the crumble on top. Cook for 45-50 minutes at 350°F/175°C, or until the middle is all the way cooked.