Season chuck roast with 1-teaspoon salt. Heat the vegetable oil in the Instant Pot set to Sauté mode, medium heat. Sear one piece of roast on its two largest sides, about 4 minutes a side; transfer to a bowl. Repeat with second piece.

Add the onions and garlic to the pot, stir in remaining 1/2 teaspoon salt and saute until the onions soften, about 5 minutes, scraping the bottom of the pot occasionally to loosen any browned bits of beef. Stir in broth and bring to a boil; cook 1 minute. Add rosemary, thyme, reserved beef with its juices and top with tomatoes.

Lock the lid, set on “Pressure Cook” mode for 70 minutes.

Let the pressure come down naturally, about 20 more minutes. Remove the lid, tilting it away from you to avoid the hot steam.

Carefully transfer beef chunks to a carving board. Discard rosemary and thyme sprigs. Strain the liquid from the pot into a fat separator. (Or just skim the excess fat with a ladle.)

Cut the roast across the grain into bite size pieces, and serve with pot sauce.