Bring a pot of water to a boil and cook the spaghetti according to package directions until al dente. Drain and set aside.
While the pasta cooks, peel and devein the prawns, then pat them dry with a paper towel.
Mince the garlic and ginger, and thinly slice the red bell pepper and green onion.
Heat the toasted sesame oil in a large wok or skillet over medium-high heat.
Add the prawns to the skillet and sear for 1-2 minutes per side until pink and opaque, then remove and set aside.
In the same skillet, add the garlic, ginger, bell pepper, and snap peas, stir-frying for 3 minutes until the vegetables are tender-crisp.
Return the prawns to the pan along with the cooked spaghetti.
Pour in the tamari and sriracha, then sprinkle with red pepper flakes.
Toss everything together for 1-2 minutes until the sauce coats the noodles and prawns evenly.
Garnish with sliced green onions and serve immediately.