Welcome to the forum!
A good place to start will be at the top of this section of the forum. Scroll to the topic at the very top, with the subject of recommended Canon lenses. Click on that, which will take you to another page, where you can click on a section for recommended portrait lenses.
The lenses that you will find there are, of course, not the only good portrait lenses. I happen to really like the 100mm 2.8L Macro lens, which is just a bit longer focal length than the oft-recommended 50mm and 85mm. I make no claim to being a portraitist, nor a "professional" photographer. Most of my "portraits," by far, however, are quite specialized, as my human subjects are usually crime victims, so I am photographing a series of images that progress from far to near, culminating in 1:1 images of specific injuries, which the macro lens allows me to do. Moreover, this "L" lens is weather-sealed, so I can use it outdoors in bad weather. Even so, there are others who like this 100mm 2.8L Macro because they prefer the 100mm focal length for portraits, anyway, and this lens has IS (image stabilization) and notably nice bokeh, the latter term referring to the pleasing effect of out-of-focus highlights, such as leaves on plants in the background.
If you are working in a studio setting, the size of your studio will affect what focal length you can use. Inside a tiny room, I can have difficulty using a 100mm lens, as I cannot find enough distance from the subject. Some professional photographers like to use very long focal lengths, such as 300mm, but their studios are huge.