Preheat the oven to 450 degrees F (230 degrees C). Spread garlic all over venison roast, season with salt and pepper, and place in a roasting pan.
Heat butter in a skillet over medium-low heat and cook and stir 1/2 cup onion, cilantro, sage, and basil until onion has softened and turned translucent, about 5 minutes. Spread the butter mixture evenly over the roast.
Roast in the preheated oven for 20 minutes. Add remaining 2 cups onion, orange juice, and cranberries to the roasting pan; reduce oven temperature to 325 degrees F (165 degrees C). Continue to roast, basting frequently, until a meat thermometer inserted into the thickest part reads 140 degrees F for medium rare, about 1 hour. Remove the roast from the pan; cover to keep warm while you prepare the sauce.
Pour beef stock into the roasting pan, and bring to a boil while scraping the browned bits of food off the bottom of the pan with a wooden spoon. Continue boiling until the liquid is reduced by half, about 10 minutes. Skim off any fat; stir in the jelly and sherry. Continue to boil until the sauce is slightly thickened and evenly coats the back of a spoon, about 3 minutes. Season with salt and pepper.
