Tri-tips cook relatively quickly in conventional ovens, but immerse one in convection heat and you'll shave about 15 percent off the cooking time. Convection ovens outperform conventional ovens in every department; quick browning and uniform doneness throughout are the first things you'll notice when you bake these three-sided cuts from the bottom sirloin with convection. You don't have to sear tri-tip on the stove first when you roast in a convection oven, either, because a torrent of hot air starts browning the surface as soon as you close the door. Determine doneness with a meat thermometer until you get accustomed to using convection.
Marinate the tri-tip for two to 12 hours in a marinade comprising 1 part food acid, such as Worcestershire sauce or soy sauce, to 3 parts olive oil. You can also marinate the tri-tip in your favorite vinaigrette.
Season the tri-tip with kosher salt if you didn't use a salty marinade. Let the tri-tip sit at room temperature for about 15 to 20 minutes.
Set the convection oven to 400 degrees Fahrenheit. Place the tri-tip on a roasting rack in a shallow roasting pan. If you want to cook vegetables along with the tri-tip, place them around the roast. Place the tri-tip in the oven.
Bake a 1 1/2- to 2-pound tri-tip for 22 minutes for medium rare, or until it reaches 125 to 130 F in the center; roast the tri-tip for 26 minutes for medium, or an internal temperature of 130 to 135 F in the center. Add five minutes of cooking time for every additional 1/2 pound.
Take the tri-tip out and let it rest for five minutes with a piece of aluminum foil tented over it. Slice the fat from the top of the tri-tip, then slice it across the grain before serving.
Salt the tri-tip on both sides with kosher salt and freshly ground black pepper. Let the tri-tip warm up to room temperature, about 20 minutes per pound, in a dish on top of a few paper towels.
Sear the tri-tip in an oiled saute pan on both sides until heavily browned, about three minutes each side. Set your heat on medium-high heat on the stove.
Transfer the tri-tip to a deep braising dish, one with a lid if possible, after you sear it. Pour about 1 cup of water or stock in the pan and scrape the bottom of it with a wooden spoon.
Pour the water or stock from the saute pan over the tri-tip. Bring about 2 cups of stock to a simmer on the stove and pour it in the dish with the tri-tip until it covers it by at least half.
Heat the convection oven to 375 F. Add any vegetables you want to braise the tri-tip with and cover the pan with the lid. You can use aluminum foil if you don't have a lid.
Turn the tri-tip over once an hour and check the stock level. Add water if necessary to cover the tri-tip be about half.
Braise the tri-tip for two hours and check the tenderness. It should separate easily with a fork. Take the pan from the oven.
Set the tri-tip aside on the serving dish with the vegetables, if any. Transfer the braising liquid to a saucepan and cook over medium-high heat on the stove until it reduces by half to three-quarters, about 15 minutes. Pour over the tri-tip and serve.