Salt both sides of the beef and let it sit for 30 minutes. This will bring out excess moisture and braises nicely. After the excess moisture is drawn out, grab some paper towel and whip the meat. Get the excess moisture and water off of it.
Set the cast iron pot over medium-high heat. Add the olive oil and get it hot. Add the pot roast and sear for 5 minutes on each side.
Remove the beef, and set it aside on a plate.
Add more oil, then add the onions. Turn the heat to medium and saute until translucent.
Add the roast back to the pot, add the garlic, and the rest of the ingredients.
Bring to a boil, cover and stick it in the oven.
Slow roast until beef is fall apart tender. This takes 1 1/2 - 2 hours, depending on the size. Just keep checking on it or take it out when it's done to your liking.