Grease an 7 or 8-inch spring form pan with butter, and line the bottom with a circle of parchment paper. Set it aside.
In a large bowl add the fruit, lemon juice, cornstarch, sugar, vanilla and cinnamon.
Toss everything together well until the fruit is coated in the sugar and cornstarch.
Pour the fruit mixture into the prepared pan and smooth out the top a little bit to make it even.
For the topping:
Add the flour, oats, sugar, cinnamon and salt to a bowl and mix together with a fork until combined.
Using your hands, add the butter to the dry ingredients and crumble the oat mixture together with the butter until the mixture resembles coarse crumbs.
Add the topping over the fruit mixture in the pan, making sure it covers the fruit mixture evenly.
Cover the pan with a double layer of aluminum foil, folding the sides of the foil tightly around the edge of the pan to form a seal.
Pour 3/4 cup of water into the bottom of the Instant Pot, place the pan on a trivet and lower it into the Instant Pot. Close the lid and turn the valve to sealing, setting the Instant Pot to cook on high pressure for 17 minutes.
Once the 17 minutes is up, release the pressure manually (quick release) then remove the pan from the Instant Pot. Remove the foil lid immediately and let the apple crisp cool in its pan on a wire cooling rack for about 10-15 minutes before serving warm with a scoop of vanilla ice cream.
Notes
This apple crisp keeps well in an airtight container for up to 2 days after baking. The apple crisp baked for this blog post was baked in an 8-quart Instant Pot Duo in an 8-inch springform cake pan. It's possible to make this apple crisp in a 7-inch round pan if you have a smaller Instant Pot (6 quart) and an 8-inch pan won't fit in your Instant Pot. You shouldn't have to adjust the pressure cooking time at all.I recommend using a spring form pan for this recipe because they have higher sides than most regular cake pans.