Domain authority is a function primarily of the quality of links that your website attracts over time.
It also grows from the natural increase of your authority as you add more content over time.
You can boost your DA by putting more effort into attracting links.
How do you do this?
Well, you can go on podcasts that are very specific to your niche.
While the audience is smaller, the people more likely to listen tend to actually be bloggers or publishers themselves.
It's a smaller community but their small number more than makes up for itself because they're more likely to link to you if they find you credible and authoritative.
Remember, when you go on a podcast, you produce a win-win situation.
They get free content but you get free linking opportunities.