Add onions, carrots, 3/4 tsp salt, and 1/2 tsp pepper to pot and cook, stirring occasionally, until vegetables are softened, 8 to 10 minutes. Add wine and zest and bring to a boil. Add beef and return to a boil. Cover pot and braise in oven until meat is very tender, 2 to 4 hours (beef cheeks take longer than chuck). Season with salt and pepper. Serve beef with carrots and sauce.