1. In a large pot of salted boiling water, cook noodles until tender, 7 to 10 minutes or until tender. Drain and set aside.
2. In a small bowl, whisk together lime juice, brown sugar, fish sauce, soy sauce, and cayenne pepper. Set aside.
3. In a large nonstick pan over medium-high heat, heat oil. Add bell pepper and cook until tender, about 4 minutes. Stir in garlic and cook until fragrant, about 1 minute more.
4. Add the shrimp and season with salt and pepper. Cook until pink, about 2 minutes per side.
5. Push the shrimp and vegetables to one side of the pan and pour in the egg. Scramble until just set then mix with the shrimp mixture.
6. Add the cooked noodles and toss until combined. Pour in the lime juice mixture and toss until the noodles are coated.
Top with green onions and roasted peanuts.