Place a trivet in a multi-functional pressure cooker (such as Instant Pot®); add 1 cup water.

Heat heavy cream in the microwave until very hot, but not boiling, about 45 seconds.

Whisk egg yolks, 2 1/2 tablespoons sugar, vanilla, and salt together in a mixing bowl. Add 2 tablespoons of the warm cream and whisk quickly. Slowly add in the remaining cream, stirring well. Pour the mixture into three 6-ounce ramekins.

Cover ramekins with foil and place on the trivet, stacking if necessary. Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 8 minutes. Allow 10 to 15 minutes for pressure to build.

Release pressure using the natural-release method according to manufacturer's instructions, about 5 minutes. Unlock and remove the lid. Check custard; it should jiggle around the edges but not be liquid; it will set up more as it cools. Let cool to room temperature, 15 to 30 minutes. Refrigerate for 4 hours.

Top each custard with 1 teaspoon sugar. Heat sugar with a kitchen torch until caramelized, about 30 seconds. Serve immediately.