Blend the flour with garlic powder, salt, and pepper in a bowl, then coat the beef cubes thoroughly in this dry mixture.
Warm olive oil over medium-high heat in a Dutch oven or large pot. Brown the flour-coated beef in batches, shaking off any excess before searing. Set aside each batch once browned.
Sauté the chopped onion in the same pot, incorporating additional oil if needed, cooking until just softened—about 3 minutes.
Deglaze the pan with beef broth and red wine, scraping up any flavorful brown bits stuck to the bottom.
Return the browned beef to the pot and stir in the potatoes, carrots, celery, tomato paste, and rosemary. Lower the heat to medium-low, cover the pot, and let simmer for about 1 hour, or until the beef becomes fork-tender (may extend up to 90 minutes).
In a small dish, combine equal parts cornstarch and water to form a slurry. Gradually stir this into the gently boiling stew to thicken, using only as much as necessary for desired consistency.
Fold in the peas and allow the stew to simmer uncovered for another 5 to 10 minutes. Season to taste with salt and pepper before serving.
Notes
If the stew meat remains tough after an hour of simmering, continue cooking covered for an extra 15–20 minutes until it reaches the desired tenderness.