Cook pasta as directed on package, reserving 1 cup of cooking liquid when draining.
Heat 2 tablespoons olive oil in a large skillet over medium. Finely chop onion and mince garlic. Add onion and half the garlic to hot oil; saute for 1-2 minutes. Add tomato sauce, salt and pepper; stir and cook for 20 minutes over low heat, stirring occasionally to prevent sauce from sticking to skillet.
Meanwhile, heat a second skillet over medium-high heat and add remaining oil. Once hot, add green beans; cook for 5-6 minutes, stirring occasionally to avoid burning. Add other half of minced garlic and sea salt; cook for 30 seconds longer, stirring to coat beans evenly. Add water, cover, and cook for 1-2 minutes. When beans are crisp-tender, remove from heat.
Remove sauce from heat; stir in cream and cheese. Add pasta and basil; stir well to coat evenly.
Serve pasta with beans on the side.