Remove 1 rack baby back pork ribs from the packaging and pat ribs dry with a paper towel. Spray the aluminum pan with nonstick cooking spray or rub with oil. Place ribs into pan. Remove silver skin from the back side of the ribs.
Sprinkle some of the 1/2 cup pork seasoning rub onto the back of the ribs. It's called 'rub' for a reason. So you want to really get in there and rub and press it in. Note: if you'd like, you can cut the rack of ribs in half to make it easier to handle on the grill later.
Flip the ribs over and season the opposite side. The rule of thumb with rub is however much naturally sticks to the ribs is enough. Whatever falls off after rubbing it in can be discarded. Pour 1 cup unsweetened apple juice into the bottom of 1 large disposable aluminum tray pan. Cover pan with aluminum foil and place into the fridge until your grill is ready.
Preheat grill to 300°F degrees. It's important to try to maintain this temperature through the cooking process so your ribs don't cook too fast. I have 3 burners and I will usually keep the middle burner off and just keep the two end burners on low so it's a nice, low, indirect heat for the ribs.
Clean the grill grates and carefully wipe them down with a bit of oil (you'll need nice, clean, nonstick grates a little later.) Place pan of ribs onto grill. Cover grill and cook for about an hour (maintaining 300°F degrees during the cooking process.) You may need up to 2 hours for these ribs so plan accordingly (especially if you are having difficulty keeping the temperature at a consistent temperature.)
Ribs are safe to eat when an inserted meat thermometer (into the thickest part of the meat – away from the bone) reaches 145°F degrees. However, we're looking for maximum tenderness so we're looking to get a temperature of 180°F – 190°F. The meat should look like it will easily pull away from the bone. Carefully remove ribs from the pan and place directly on the grill. Ensure heat stays on low.
Meanwhile, in a small pot over medium heat, whisk together 1/2 cup orange marmalade and 1/4 cup apple cider vinegar. Continue to whisk until it's combined well. This should only take a minute or two. You can do this on the grill if you have a side burner attached to your grill.
Take pot off heat and baste the cooked ribs with the marmalade sauce. Make sure to coat it well.
Cover grill and cook for an additional 5 minutes. Then repeat the process one more time. Carefully remove the ribs off the grill and place on a large cutting board and allow the meat to rest and cool for a few minutes.
With a sharp knife, carefully cut the ribs between the bones and serve!