Begin by coating the stewing beef with a light dusting of flour, and generously seasoning with salt and pepper.
In a large, heavy-based Dutch oven or saucepan, heat olive oil over high heat. Once the oil shimmers, sear the beef on all sides until it's a golden-brown. Once seared, remove the beef and set it aside.
Lower the heat to low, and add more oil if needed. Add in the chopped onions and your diced celery. Let them sauté, stirring occasionally, until the onions achieve a slight translucence.
Add the minced garlic, dried rosemary, and chili flakes and let them harmonize for about a minute.
Bring back the seared beef along with any juices it left behind in to the pot. Add the crushed canned tomatoes and the beef stock and stir.
Cover the pot and let simmer on low for 1-1.5 hours, allowing the beef to tenderize and the flavors to infuse. Stir occasionally to ensure nothing sticks to the bottom.
As the beef nears perfection (about 45 minutes), it's time to introduce the zucchinis and red bell peppers to the mix. Add them and cook for an additional 30 minutes, stirring occasionally.
If the stew seems to yearn for a bit more liquid, you can introduce a touch of water to the mix, adjusting to your preferred level.
In the last 10 minutes add the Kalamata olives and chopped fresh parsley.
Taste and adjust the notes as needed - more salt, more pepper, or a touch more chili flakes, all tailored to your palate's preferences.
Serve this Beef Stew with your choice of rice, mashed potatoes, or a toasted baguette.