01 - Preheat the oven to 325°F.
02 - Pat beef cubes dry and season generously with salt and pepper.
03 - Heat olive oil in a large Dutch oven over medium-high heat and sear beef cubes in batches until browned on all sides. Transfer to a plate.
04 - Reduce heat to medium. Add sliced red onions, carrots, and celery to the pot. Sauté for 8 to 10 minutes until onions soften and caramelize slightly.
05 - Stir in minced garlic and tomato paste, cooking for 2 minutes until fragrant.
06 - Return beef to the pot. Pour in red wine and bring to a simmer, scraping any browned bits from the bottom.
07 - Add beef stock, bay leaves, and thyme. Stir and bring to a gentle simmer.
08 - Cover the pot and transfer to the preheated oven. Braise for 2 to 2.5 hours, or until beef is fork-tender.
09 - Remove bay leaves and thyme sprigs. Adjust seasoning with salt and pepper to taste.
10 - Plate hot and garnish with chopped parsley if desired.