1. Bring a lg. pot of salted water to a boil. Meanwhile, in a lg. skillet, heat 1 tbsp oil over med-high. Season beef with salt n pepper; and half the beef to skillet. Cook, without stirring, until browned on one side, 1 to 2 mins. Transfer to a plate (meat will cook more later), and repeat with remaining tbsp oil and remaining beef. Set beef aside, reserving skillet.
2. Add onion, bell peppers, and 1/4 cup water to skillet; season with salt and pepper. Cook, stirring occasionally, until vegetables are crisp-tender, 3 to 4 mins. Add curry paste; cook, scraping bottom of skillet, 1 min.
3. Return beef to skillet, with any accumulated juices, and add coconut milk. Simmer until sauce thickens slightly, 4 to 5 mins. Remove from heat. Stir in basil and lemon juice, and season curry with salt and pepper.
4. Add pasta to boiling water, and cook untl al dente, according to pkg. instructions; drain. Serve beef curry over pasta.