To make the lime and chilli butter, place the butter in a small bowl. Add the lime zest, chilli flakes and a pinch of salt and pepper. Using a spoon, mix thoroughly together. Work the butter into two small disc shapes and place in the fridge while you get on with prepping the pot.
Pour one cup (240ml) of water into the Instant Pot. Place the steam rack inside, making sure that the handles are extended upwards. Tear off a piece of baking parchment big enough to fit the salmon fillets. Place the salmon fillets on top of the parchment and place the butter discs on top of each fillet. Season the salmon with salt and pepper. Gather the sides of the parchment up over the salmon and scrunch the top pieces together to make a secure parcel (you don't want all that lovely butter to escape) Place the wrapped salmon on top of the steam rack.
Place the lid on the Instant Pot, make sure the vent is set to "SEALING" and press the steam button. Using the - or + buttons, set the timer to 3 minutes.
Once the timer has finished and the Instant Pot beeps, your salmon is ready. Using a pair of tongs or something similar, do a quick release pressure (turn the seal to "VENTING" taking care not to catch yourself on the hot steam that will be released (I wear a pair of oven gloves while doing this) Press the "KEEP WARM/CANCEL" button and carefully remove the lid of the pot. Carefully remove the salmon parcel from the pot and transfer to a plate. Serve with steamed new potatoes, veg of your choice and pour over all the lovely buttery juices.