Preheat oven to 400°F. Place the cherry tomatoes in an oven-safe baking dish. Pour ¼ cup olive oil on top, and season with salt and pepper. Toss until well combined.
Place the feta block in the middle of the baking dish surrounded by the cherry tomatoes and flip a couple times to coat it with the olive oil and seasoning.
Bake in the preheated oven for 35-40 minutes, until the cherry tomatoes burst, and the feta cheese melts
While the feta is baking, heat remaining 1 tablespoon olive oil over medium heat. Add the onions and cook until soft and translucent, 5 minutes. Season with salt, pepper, and crushed red pepper (if using). Add the garlic, canned tomatoes, stock and thyme, and let gently simmer until tomatoes in the oven are done roasting
Once tomatoes and feta in the oven are done, transfer to the simmering pot. Season with salt and pepper, to taste and add the basil. Bring the soup back to simmer and add orzo. Simmer until orzo is fully cooked, 7-8 minutes. Serve with more crumbled feta, basil, and black pepper.
Notes
Storage: If making ahead of time, it's best not to add the orzo until you are ready to serve. Without the pasta, the soup will keep well refrigerated for 4 to 5 days and frozen for up to 6 months.