Pat the beef chuck cubes dry with paper towels. Season generously with 1 tsp salt and 0.5 tsp black pepper.

Heat 1 tbsp of olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Working in batches to avoid overcrowding, brown the beef on all sides until a deep brown crust forms, about 3-4 minutes per batch. Remove browned beef to a plate and set aside.

Add the remaining 1 tbsp of olive oil to the pot (add more if needed). Reduce heat to medium. Add the chopped onion and cook, stirring occasionally, until softened and translucent, about 5-7 minutes. Add the minced garlic and tomato paste, cooking for another 1-2 minutes until fragrant.

Pour in the red wine (if using) and scrape the bottom of the pot with a wooden spoon to loosen any browned bits. Let the wine simmer and reduce for 2-3 minutes. Stir in the crushed tomatoes, beef broth, oregano, thyme, bay leaf, cinnamon, and red pepper flakes (if using).

Return the browned beef and any accumulated juices to the pot. Bring the mixture to a gentle simmer, then reduce heat to low, cover the pot, and cook for 90-105 minutes, or until the beef is very tender and easily pierced with a fork. Stir occasionally to prevent sticking.

Once the beef is tender, uncover the pot. Increase heat to medium-low. Stir in the uncooked orzo pasta. Continue to simmer, uncovered, for 15-20 minutes, stirring frequently to prevent the orzo from sticking to the bottom, until the orzo is al dente and most of the liquid has been absorbed. If the mixture becomes too dry before the orzo is cooked, add a little more beef broth or water, about 1/4 cup at a time.

Remove the bay leaf. Taste and adjust seasoning with salt and pepper as needed. If desired, stir in 2 tbsp of unsalted butter for extra richness. Ladle the One Pot Beef Giouvetsi into bowls, garnish with fresh chopped parsley, and serve hot, optionally topped with crumbled feta cheese.