In a large bowl, whisk together butter, eggs, flour, baking powder, cocoa powder, salt, and sugar. Do not overmix. Fold in chocolate chips and pecans. Pour batter into a greased 6 inch cake pan. Cover pan with a piece of aluminum foil.
Pour water into the Instant Pot®. Set trivet in pot. Place cake pan on top of the trivet. Lock lid.
Press the Manual button and adjust time to 20 minutes.
When timer beeps, let pressure release naturally for 5 minutes. Quick-release any additional pressure until float valve drops and then unlock lid.
Remove cake pan from the Instant Pot® and transfer to a rack to cool. Sprinkle with powdered sugar and serve.