Buy precooked peeled and deveined shrimp. Prepare the dressing while noodles cook, and toss together for a supersimple, fresh-tasting meal.
Cook pasta according to package directions, omitting salt and fat; drain.
Combine lime juice and next 6 ingredients (through garlic) in a small bowl, stirring to combine.
Combine pasta and shrimp in a large bowl. Drizzle with dressing; toss to coat. Sprinkle with onions. Serve immediately with lime wedges, if desired.