In a large bowl, combine the garlic, onions, orange juice and lime juice. Set aside.
Heat the oil in a large sauce pan until you see the first whiff of smoke. Now, cover your arms and, wearing oven mitts, carefully slide the contents of the bowl into hot oil. Be very careful as the liquid will splatter. Dinosaur BBQ recommends this step because it produces superior flavor release. Simmer for 5 minutes to soften the onions and garlic.
Season the marinade with the remaining spices and seasonings. Stir and remove from heat.
Pour the marinade into a blender or a food processor and pulse 3 times to combine the ingredients.
Transfer the finished marinade into a plastic container and cool to room temperature. Then cover and refrigerate. The marinade can be stored in a fridge for up to 2 weeks.