Peel and slice the yellow onions. There is no need for them to be perfectly thin, but make the slices even. Lay them onto a baking sheet lined with tinfoil, and lay the sprigs of thyme on top (so that way easier cleanup).
Peel and thinly slice your garlic cloves.
Pat dry your prime rib, and place on top of the sliced onions. Using a paring knife, make small incisions all over the top of your prime rib. Slip into each incision one slice of garlic clove per incision. This is to perfume the meat from the inside-out.
Make a paste with the olive oil and the salt. The salt should make the olive oil into a paste. Massage the paste into the meat.
Place into the oven. For each bone, cook for 15 minutes at 500 degrees (ex: 4 bones x 15 minutes = 1 hr). After the X amount of time has passed depending on your roast, turn off the oven. DO NOT OPEN THE DOOR. All the roast to stay in the oven for one more hour with the oven turned off.
Remove after one hour turned off. Let rest.
Red Wine Sauce
While your meat is cooking and resting, prepare the wine sauce.
Heat a sauce pan with the oil. Once it is heated, add the onions until lightly browned. Add the herbs and deglaze the pan with the red wine. Add beef broth.
As Anne Burrell says, BTB, RTS! (Bring to boil, reduce to simmer). Reduce until it is as thick or thin to your liking! I like mine more of the syrupy side.