Rinse rice with water through a mesh strainer or colander.
Set Instant Pot {6 quart} to saute setting and let it get hot.
Add in bacon grease or vegetable oil and onion and cook until translucent, about 1 to 2 minutes.
Add in the rice and saute for 2 minutes.
Stir in chicken stock, salt, and pepper. Stirring and scraping bottom to be sure to get any stuck bits up.
Pour in can of diced tomatoes.
Lock lid and set to manual high pressure for 10 minutes.
Once time is up, manually release (turning or pressing valve to open).
Fluff the rice and tomatoes with a fork and serve.
Notes
If you do not have bacon grease on hand, you can saute cut up bite sized bacon pieces and render the fat. Remove bacon and drain on paper towels to use for garnish.