In the inner pot, add the minced onion, minced garlic and beef broth. Place the rack inside the pot and set aside.
Cut the pork ribs into 3 sections per slab and set aside.
In a small bowl, combine the paprika, salt, black pepper, chili powder and cayenne pepper.
Rub dry rub mixture evenly over ribs. Stand the ribs vertically on top of the rack in the pot.
Close and lock the lid and turn the steam release handle to Sealing. Set your Instant Pot to pressure cook on High for 25 minutes.
When the timer beeps, press Cancel and let the pot stand, covered, for 5 minutes. After 5 minutes, turn the steam release handle to Venting and remove the lid. The ribs should be fork tender and almost ready to fall off the bone. (If more cooking is needed, reset the manual pressure to High for 5 minutes.) Transfer ribs to a serving platter and tent with foil to keep warm.
Discard all but ½ cup of the liquid in the pot. Skim off any fat. Press Sauté.
Stir in ketchup, vinegar, Worcestershire and mustard. In a small bowl, whisk together cornstarch and cold water. Stir the cornstarch mixture to the pot.
Cook sauce, stirring, for 4 minutes or until sauce is thickened. Season to taste with salt and pepper.
Brush sauce over ribs. Serve any remaining sauce in a bowl on the side.
Tips For Best Results
Cook Ribs Until Fork Tender. Fall-off-the bone is not a good term when used with BBQ ribs. Ribs that fall off the bone are overcooked. While they may taste okay, you want to be able to eat the meat from the bones like ribs are meant to be eaten. Cook the Instant Pot Baby Back Ribs according to the directions. You can always add more cooking time if needed.
Do Not Marinate. You should not soak the ribs in vinegar. Vinegar can turn the pork meat into mush. Cooking in the Instant Pot is all you need to tenderize your ribs to perfection.
Do Not Overfill the Instant Pot. You can fit up to 2 racks of ribs in the Instant Pot for best results. Add more ribs to the pot and you risk them cooking unevenly.
Determine Serving Sizes. This ribs recipe serves 6 people with 2 racks of ribs which weight approximately 3-½ to 4 pounds total. Each full rack will have on average 12 rib bones. So with 2 racks of baby baby ribs you will have about 24 ribs, or 4 ribs per person. For 8 people you will need 3 racks of ribs. The suggested serving sizes depend on the number of side dishes and appetizers. Also factor in the mix of people you are serving.
Cover BBQ ribs tightly and refrigerate for up to 5 days. You may want to store them in an oven-safe glass storage container. Then, reheating them in the Instant Pot is super easy and makes for one less dish to wash.
Reheat ribs in the Instant Pot. Place the steam rack (the one that came with your Instant Pot) inside the pot and add 1 cup of water to the pot. Arrange the ribs in a glass food storage dish (see tip above) and place on the rack. Close and lock the lid. Steam cook on high for 5 minutes. Check the ribs and add more time if needed to warm them throughout.