01 - Set the oven to 400°F to prepare for roasting.
02 - In a large ovenproof baking dish, combine whole cherry tomatoes, sliced garlic, and red onion if using. Drizzle with 2 tablespoons of olive oil, season with salt, pepper, and crushed red pepper flakes, then toss to coat evenly.
03 - Place the block of feta cheese in the center of the tomato mixture and drizzle remaining 1 tablespoon of olive oil over the feta.
04 - Bake in the preheated oven for 30 minutes, until tomatoes blister and feta softens and turns golden.
05 - While roasting, cook the pasta in salted boiling water according to package instructions until al dente. Reserve ½ cup of the pasta cooking water, then drain the pasta.
06 - Remove the baking dish from the oven. Use a fork to mash the roasted feta and tomatoes to form a creamy sauce.
07 - Add the drained pasta and half of the basil into the baking dish. Toss to combine, adding reserved pasta water as needed to achieve a smooth consistency.
08 - Dish out immediately, garnishing with remaining basil leaves and an extra sprinkle of black pepper.