Whisk together lemon juice, olive oil, brown sugar, soy sauce, salt, Worcestershire sauce, black pepper, garlic, and chili powder in a small bowl.
Place trip-tip in a large resealable bag and pour in the marinade. Seal bag, removing as much air as possible. Place in refrigerator and marinate 6-8 hours. Or overnight for optimal flavor.
In a medium bowl add sliced peppers and onions add olive oil salt and pepper and toss until combined. Set aside.
Heat a gas or charcoal grill on medium-high heat. Remove beef from marinade and place directly over coals for 5-6 minutes then flip and cook another 5-6 minutes or until you get a good sear. Move Tri-Tip to indirect heat and cook covered for 25-30 minutes or until desired doneness. Then check the temp with a meat thermometer by placing it into the thickest part (*see notes), grill to desired doneness 120°F for rare, 130°F for medium-rare, and 140°F for medium
Heat the olive oil in a skillet on medium-high heat and add the onion and peppers. Saute for 10 minutes or until desired softness. See notes
Let meat rest 10-15 minutes. Slice into thin slices against the grain.
Notes
If you have a cast-iron skillet you can place that on the grill and cook the onion and peppers there.Be sure to slice the tri tip in thin slices against the grain, you will have to turn it as the grain will change about halfway up the tri tip.The tri tip is shaped like a triangle so the skinny part will be cooked more then the thick part.