Bring a large pot of salted water to a boil. Wash and dry all produce. Core, deseed, and thinly slice bell pepper. Trim and thinly slice scallions, separating whites from greens. Trim and peel carrot. Using peeler, shave carrot lengthwise into ribbons, rotating, until you get to the core; discard core. Zest and quarter lime (quarter both limes for 4 servings). Peel and grate ginger. Grate 1 clove garlic (2 cloves for 4).

Once water is boiling, add spaghetti to pot. Cook, stirring occasionally, until al dente, 9-11 minutes. Drain well. (TIP: Shake strainer to remove excess water.) Meanwhile, add sesame seeds to a large, dry pan over medium-high heat. Toast, stirring, until golden brown, 2-3 minutes. Turn off heat; transfer to a small bowl.

Heat a large drizzle of oil in same pan over medium-high heat. Add bell pepper and cook, stirring occasionally, until tender, 6-8 minutes. Add carrot ribbons and scallion whites. Cook, stirring, until softened, 1-2 minutes. Turn off heat.

Meanwhile, massage peanut butter in packet to loosen. (TIP: If peanut butter is very cold, squeeze into a small, microwave-safe bowl. Microwave until softened, about 20 seconds.) In a large bowl, whisk together peanut butter, sesame oil, soy sauce, lime zest, ginger, garlic, half the vinegar (use all for 4 servings), juice from 2 lime wedges, and 1 TBSP sugar (2 TBSP for 4) until smooth.

Roughly chop peanuts. Add noodles, veggies, half the sesame seeds, and half the peanuts to bowl with sauce; toss with tongs to combine. (TIP: If noodles are not fully coated in sauce, add water a splash at a time to bowl and continue tossing.) Season with salt.

Thinly slice chili, removing seeds for less heat. Divide noodles between shallow bowls. Top with scallion greens and remaining sesame seeds and peanuts. Sprinkle with a pinch of chili if desired. Serve with remaining lime wedges on the side.