How to replace default font in CKEDITOR?

Question

JavaScript

Good evening, I have a question.
How to make span with custom font appear with default font.
At the moment, with default, a tag is created. If you select a font, the following is created:<p>Текст</p>

<p><span style="font-style:'Arial'">Текст</span></p>

I would like the default to be the same as when choosing a font.
The font you want to be default: Open Sans.