Set Instant Pot to saute; add olive oil, onion, garlic, salt, fennel seeds, oregano, pepper, and red pepper flakes.
Cook, stirring occasionally, until onion is softened, about 5 minutes.
Add red wine; stir to release browned bits. Simmer 2 minutes.
Add tomatoes, bay leaves, brown sugar, and Parmesan rind, if using.
Press Cancel to reset Instant Pot.
Place top on Instant Pot; twist to seal and lock. Turn Steam Release Valve to “sealing.”
Set Instant Pot to cook at High Pressure for 10 minutes.
After cooking is complete, let pressure release naturally (about 10 minutes). After that, manually release the pressure by turning the Steam Release Valve to “venting.”
Remove lid from Instant Pot; hit Cancel to reset.
Stir in vinegar. Taste, and add salt as desired.
If a thicker sauce is desired, set Instant Pot to saute and simmer 10 to 15 additional minutes.
Remove and discard bay leaves and Parmesan rind, if using.
Use immediately, refrigerate up to 3 days, or freeze up to three months.