I saw it done on this show but I can't find the full episode!
Feed the cat and the dog with a solid door between them a bedroom maybe. You'll need a second person in the room with the cat.
You can just put the dog's food outside the door. The cat's food you need to see how close you can get the cat's bowl to the closed door. They can smell each other and that's the goal.
When you can get the cat to finally eat very close to the closed door then you can move to the next step a baby gate. Same deal once again and start over for distance, dog close and move the cat closer to the gate. Soon as they can eat close to each other then you can try feeding then in the same room.
When they can be in the same room I would feed the cat high and the dog low..and make sure the cat has save places when they are in the same room no point in pushing it!
Mostly what went wrong was you moved to fast, the dog was new the cat didn't trust him and unfortunately "that" cats first reaction was not to run!
So you have to build a relationship of trust between the two of them.
You also need to bond better with the dog. The dog should "stay" when you tell him to more obedience exercise games and bonding time required,
But a stay is out the window for this cat/dog situation so the door thing is a better option. Did I explain it well enough? Ask questions if your unsure.
I saw this on TV a couple of weeks ago but I can't find the full episode, My Cat from ****, is the show.
Also I guess it goes without saying, don't hold the cat in the dogs presence!