In a blender, combine the olive oil, neutral oil, soy sauce, vinegar, honey, tahini, garlic, ginger (no need to peel it) and 1/2 tsp. salt. Blend on high speed until smooth, 30 to 45 seconds.

Place the steak in a resealable plastic bag or a large bowl. Add enough marinade just to cover the steak, about 1/4 cup (2 fl. oz./60 ml). Let marinate at room temperature for at least 30 minutes or in the refrigerator for up to 48 hours. Cover and refrigerate the remaining marinade (which will become your sauce) until dinnertime.

Meanwhile, cut the bell peppers into thin strips.

Position a rack in the top of the oven and heat the broiler to high. Line a rimmed baking sheet with aluminum foil. Alternatively, heat a stovetop grill pan over medium-high heat.

Remove the steak from the marinade, letting any excess drip off. Pat it dry and sprinkle with about 1 tsp. salt.

If using a broiler, place the steak on one side of the baking sheet. Place the peppers on the other side. Add 2 to 3 Tbs. of the marinade and toss to coat well. Broil for 4 minutes, then flip the steak and stir the vegetables. Broil until an instant-read thermometer inserted into the steak registers 125° to 130°F (52° to 54°C) for medium-rare, about 4 minutes more. Transfer the steak to a cutting board to rest for at least 5 minutes.

If using a stovetop grill pan, place the steak and in the pan and toss the with 2 to 3 Tbs. of the marinade. Cook, flipping the and stirring the vegetables halfway through cooking, until the registers 125° to 130°F (52° to 54°C) and the are tender and lightly charred. Let the rest as directed above.