Create text overlay on a map

I now have a basic map showing on my public website, I am slowly converting my old Google maps code to Tomtom but would like first to put a simple text message inside a rectangular box with a white background at the center of the map to let my viewers know I am working on enhancing the expected maps.

I have looked at many of the 100+ examples but haven’t seen anything like a simple text box. I have seen text inside popups.

Do I have to define a Marker with a Popup on the map object to get such a text box overlay?

I’ve created an example. It is available here:
Let me know if that is sufficient for you.

Thank you so much, Przemek!