This crowd pleasing recipe is a snap to prepare. While the juicy Tri-Tip Roast rests after cooking, you can get the broccolini side dish and creamy sauce ready.
Combine marinade ingredients in small bowl. Reserve 2 tablespoons for basting. Place beef Tri-Tip Roast and remaining marinade in foodsafe plastic bag; turn roast to coat. Close bag securely and marinate in refrigerator 30 minutes to 2 hours.
Heat oven to 425°F. Remove roast from marinade; discard marinade. Place roast on rack in shallow roasting pan. Place onion wedges around roast. Do not add water or cover. Roast in 425°F oven 30 to 40 minutes for medium rare; 40 to 50 minutes for medium doneness, basting with reserved 2 tablespoons marinade halfway through roasting time.
Remove roast when instant-read thermometer registers 135°F for medium rare; 150°F for medium. Transfer roast to carving board; tent loosely with aluminum foil. Let stand 20-25 minutes. (Temperature will continue to rise about 10°F to reach 145°F for medium rare; 160°F for medium.)
Meanwhile prepare Creamy Gorgonzola Sauce. Combine all sauce ingredients in small bowl; mix well. Set aside.
Spray Broccolini with nonstick cooking spray, tossing to coat. Place on metal baking sheet. Roast in 425°F oven 10 to 15 minutes or until crisp-tender and slightly browned. Toss onion wedges with Broccolini. Season with salt and pepper, as desired.
Carve roast across the grain into thin slices. Season with salt and pepper, as desired. Top beef with Creamy Gorgonzola Sauce. Serve with vegetables.