1Cook pasta as directed on package; drain, reserving 1/2 cup cooking water. Return pasta to saucepan; cover to keep warm.
2Meanwhile, in large skillet, melt butter over medium heat. Cook onion and garlic in butter about 5 minutes, stirring frequently, until onion has softened. Add sun-dried tomatoes, oregano, pepper flakes, salt and capers. Cook 3 minutes longer.
3Stir in shrimp. Cover; cook until shrimp just turn pink, about 5 minutes. Stir in lemon juice. Gradually stir in reserved pasta cooking water.
4Add pasta to skillet; toss with shrimp and sauce. Serve immediately.