Bring a medium saucepan of salted water to boil. Drop tomatoes into water and boil 30 seconds. Using a slotted spoon, transfer tomatoes to a bowl; peel, seed and chop.

Heat grill or grill pan to medium-high. Grill zucchini until just tender, about 2 minutes per side. Transfer to a cutting board and dice.In a large bowl, stir together tomatoes and their juices, zucchini, 1 cup basil, oil and garlic; season generously with pepper. Let marinate at room temperature for 1 hour. Thinly slice remaining basil.

Bring a large pot of salted water to boil. Add spaghetti and cook until al dente. Drain and add to bowl with vegetables; add ricotta and sliced basil, and toss to combine. Season with salt and serve at once.