One of my summer staples! We use this for pasta, but also for sandwich spreads, bruschetta, or eating straight with a spoon. It'll make more than 1 cup (about 1.5), but for whatever reason, I can't enter half cups here.
Add the basil and parmesan to the bowl of a food processor or a blender. Pulse until well combined. Add salt. Scrape down the sides of the machine.
With the food processor running, drizzle in the olive oil. After it's all added, you may need to stop the machine and scrape down the sides, then continue to process until all combined and desired consistency has been reached.