Prep the pan: Grease the cake pan well. Line the bottom with a circle of parchment for extra insurance, then grease the parchment, too.

Make the caramel layer: Melt 4 tablespoons butter. Stir in the brown sugar until glossy. Spread this mixture evenly across the bottom of the pan.

Arrange the apples: Toss apple slices with lemon juice. Fan them over the caramel in a neat, overlapping pattern. Keep it snug—apples shrink as they cook.

Whisk dry ingredients: In a bowl, combine flour, baking powder, salt, cinnamon, and nutmeg. Set aside.

Mix wet ingredients: In another bowl, whisk egg, granulated sugar, melted 2 tablespoons butter, milk, and vanilla until smooth.

Combine: Add dry ingredients to wet and stir just until the flour disappears. The batter should be thick but pourable. Don’t overmix.

Fill the pan: Spoon batter over the apples and spread gently to the edges. Tap the pan once on the counter to settle it.

Cover: Wrap the top tightly with foil to prevent condensation from dripping onto the cake.

Set up the cooker: Pour 1 cup of water into the pressure cooker. Place the trivet inside. Lower the cake pan onto the trivet using a sling or carefully with tongs.

Cook: Seal the lid and set to high pressure for 35 minutes (for a 7-inch pan; 8-inch may need 30–32 minutes because of the thinner layer).

Release pressure: Let pressure naturally release for 10 minutes, then quick release any remaining steam.

Check doneness: Uncover and insert a toothpick into the cake portion (not the apples). It should come out clean or with a few moist crumbs. If wet, re-cover and cook 3–5 minutes more.

Cool briefly: Let the cake rest in the pan for 10 minutes. Run a thin knife around the edge.

Invert: Place a serving plate over the pan and flip confidently. Lift the pan and peel off the parchment. If any apples stick, just nudge them back on.

Serve: Spoon any caramel from the pan over the top. Serve warm with vanilla ice cream or lightly sweetened whipped cream.