01 - Set the oven to 400°F.
02 - In a large ovenproof dish, combine cherry tomatoes, garlic, and red onion if using. Drizzle with 2 tablespoons olive oil, season with salt, pepper, and red pepper flakes, then toss to coat evenly.
03 - Place the feta block in the center of the tomatoes and drizzle the remaining 1 tablespoon olive oil over the cheese.
04 - Bake for 30 minutes until tomatoes blister and feta becomes golden and soft.
05 - Meanwhile, cook pasta according to package instructions until al dente. Reserve ½ cup pasta water, then drain the pasta.
06 - Remove the baking dish from the oven. Mash the feta and tomatoes together with a fork to create a creamy sauce.
07 - Add drained pasta and half of the basil to the sauce. Toss, adding reserved pasta water as needed for a smooth consistency.
08 - Serve immediately, garnished with remaining basil and extra black pepper.