Peel your lemons taking just the yellow part, not the white one, which is bitter.
Place 2 peels into each jar.
Pour Vodka into the jars (they shall be ¾ filled).
Close the jars with their lids.
Pour 1 cup water into your Instant Pot, then place the steamer rack inside.
Place your jars onto the streamer rack.
Cook at high pressure for 30 minutes.
In the meantime, heat water in a saucepan and slowly add sugar while stirring, to obtain a syrup.
Let the steam release naturally for as long as it takes (don’t speed up this part of the process for safety reasons).
Let your jars cool at room temperature.
Open the jars and remove lemon peels.
Pour your sugar syrup into the jars.
Keep your limoncello in the fridge and serve cool.