Make sure tri-tip is dry and score the fat layer with a knife, cutting through the fat, but not through the meat. Season it with salt and pepper, then set aside.
Mix together garlic, thyme, paprika, basil, 1 tbsp oil, red wine, onion powder, salt, and black pepper.
Rub the wine marinade over meat and place in a resealable plastic bag, scraping in all the garlic paste and seal. Refrigerate for 1 hour and let it sit at room temperature 5 minutes before use. Reserve marinade and set aside.
Preheat oven to 425°F.
In a large cast-iron skillet, heat 1 tbsp olive oil over high heat and place tri-tip fat side down. Lower heat to medium-high and cook for 4-5 minutes or until thoroughly browned. Flip tri-tip and cook for 2 more minutes, then transfer to the pre-heated oven.
Roast for about 15-20 minutes or longer , depending on the weight of the tri- tip . It is best to use a meat thermometer to check for doneness . The internal temperature is 135 degrees for medium-rare and 145° for medium. Let cool for 5-10 minutes and cover with aluminum foil to keep warm.
Meanwhile, while the tri tip is roasting, place the reserved marinade in a small sauce-pan over medium-high heat. Bring the mixture to a boil and cook until thickened and reduced down. Adjust with salt and pepper.
Slice the roast against the grain Serve with the marinade sauce.