Grease a 6-inch springform pan or cake pan that fits in your Instant Pot. Line the bottom with parchment for extra safety.
In a medium bowl, whisk together ricotta, sugar, egg, lemon zest, lemon juice, and vanilla until smooth.
Sprinkle in flour, baking powder, and salt. Stir until just combined—don’t overmix.
Pour batter into prepared pan. Cover tightly with foil.
Add 1 cup of water to the Instant Pot and place pan on a trivet inside.
Pressure cook on High for 35 minutes. Let pressure naturally release for 10 minutes, then quick release the rest.
Let cake cool for 15–20 minutes before removing from pan. Chill in the fridge for a firmer texture, or enjoy slightly warm.
