When the Instant Pot reads hot, add the ground beef.
Cook, stirring to break up the meat, until the meat has browned.
Stir in the onion, and cook until softened, about 3 minutes.
Add the garlic, and cook, stirring the entire time, for 30 seconds.
Press cancel.
Add ½ cup broth, and stir to scrape up any browned bits from the bottom of the pan.
Add the pasta, and pour the remaining 1 and ½ cups broth over the pasta.
Add the diced tomatoes with juice, tomato paste, and Italian seasoning. Do not stir.
Close and lock the lid. Be sure that the pressure release vent is set to sealing.
Press manual high pressure, and adjust the cooking time to 4 minutes.
When the cooking time has finished, carefully do a controlled quick release.
Unlock and remove the lid.
Give the pasta a good stir.
Add the heavy cream, and stir in.
Season with salt and pepper to taste.
Notes
I use 85 or 88% lean ground beef in this recipe. It's lean enough that there isn't a lot of fat but not so lean that it dries out.
Ground Italian sausage would also work well in this recipe.
I like to use reduced-sodium beef broth to lower the sodium level.
For less noticeable pieces of tomato, use petite diced tomatoes.
If you use a smaller shape of pasta, like elbow macaroni, decrease the cooking time to 3 minutes. If you're using a larger shape, like rigatoni, increase the cooking time to 5 minutes.
The recipe can be doubled in a 6 quart Instant Pot. There's no need to adjust the cooking time; the pot will just take longer to come to pressure.