Put water and broccoli in the Instant Pot pressure cooker.
Close the lid and turn the valve to Sealing position.
Select the "Pressure Cook" or "Manual" button, and set the time to zero (yes, the actual cooking time is zero minutes, the broccoli is completely cooked while the Instant Pot is building up pressure).
When the Instant Pot is finished building up pressure (about 5 minutes), it will beep when ready (since the cooking time is set to 0). Quick release (QR) the steam immediately and drain the broccoli into the colander, and run the cold tap over over it to stop the cooking process (do not wait to take out the broccoli from the Instant Pot, so the broccoli doesn't get overcooked).
Sprinkle steamed broccoli with salt and pepper to taste.
Notes
You can put any amount of broccoli in the Instant Pot (doesn't have to be 2 cups), but the amount of water remains the same (1/2 cup water).