01 - Preheat the oven to 400°F. In a large ovenproof baking dish, combine cherry tomatoes, garlic, and red onion if using. Drizzle with 2 tablespoons olive oil, season with salt, pepper, and crushed red pepper flakes, then toss to coat evenly.
02 - Place the block of feta cheese centrally atop the tomatoes and drizzle with the remaining 1 tablespoon of olive oil.
03 - Bake for 30 minutes until tomatoes blister and feta becomes soft and golden.
04 - While roasting, cook pasta in salted boiling water until al dente according to package directions. Reserve ½ cup pasta cooking water and drain the rest.
05 - Remove baking dish from oven. Use a fork to mash the feta and roasted tomatoes into a creamy sauce. Add the drained pasta and half the basil to the dish, tossing together and incorporating reserved pasta water gradually to achieve a silky consistency.
06 - Plate the pasta and garnish with remaining fresh basil and additional black pepper to taste. Serve immediately.