Boil water in large skillet set over high heat. Cook pasta until al dente (cook slightly less than package directions). Reserve 1/2 cup (125 mL) pasta cooking water. Drain pasta; set aside. Heat 1 tbsp (15 mL) oil in same skillet set over medium heat. Add shrimp and hot pepper flakes; sauté 3 to 4 min. until shrimp are pink and firm. Transfer to plate.
Heat remaining oil in skillet. Add onion and garlic. Cook about 2 min. to soften. Stir in tomatoes, 1/2 cup (125 mL) water (not the pasta water), salt, pepper and oregano; bring to a boil. Reduce heat to medium-low; simmer about 15 min. until sauce is thickened. Add pasta, reserved pasta water and shrimp into skillet; stir to coat. Just before serving, stir in arugula and lemon juice; sprinkle with parsley.
For Spanish-inspired pasta, add sweet smoked paprika, green olives and cilantro.