Possible to ski from Selva to Cortina and back?

The Dolomites is my go-to area for long ski days, amazing scenery and everything else.

This year I'll be in Val Gardena and I'm wondering if it's possible to ski from there to the Tofana in Cortina and back, in a day?

I've seen Ustariapost on YouTube do it from Badia. Is Selva a valley too far?

If you can get there from Badia then you can do it from Selva too, as Val Gardena (Selva's valley) is just one along from Alta Badia. However, as you rightly imply, it would be a very long day, skiing without much of a break, so maybe theoretically, yes, you can do it, but in practice, it would be quite challenging, (and if you miss the last lift in one of those valleys, then getting home by taxi ain't cheap!)

Recommend you stop overnight at Refudio Lagazuoi. Gives you time to ski Cinque Terra. I've done it twice from Corvara.