Salt the stew beef with 2 teaspoons of the salt and add it to the Instant Pot.
Add the remaining ingredients EXCEPT FOR THE CORNSTARCH to the Instant Pot and stir to combine the ingredients.
Set the Instant Pot to “Manual” for 35 minutes. Once done, let the Instant Pot depressurize naturally.
Using a slotted spoon, scoop out the meat and majority of the vegetable (leaving some bits of the onions, carrots and tomatoes behind in the sauce) into a large bowl and cover with aluminum foil.
Set the Instant Pot to “Saute” and sauté the sauce for 10 minutes then turn off the Instant Pot. Transfer the sauce to a blender and blend on high until smooth. Return the sauce to the Instant Pot and tun off the "Sautee" function.
In a small bowl, combine the cornstarch with 2 tablespoons of water to create a slurry. Slowly pour the cornstarch slurry into the sauce and stir to combine, the sauce will slightly thicken.
Add the meat and vegetables back into the Instant Pot.
Serve over mashed potatoes or spaghetti squash.