Cut the beef into 4cm (1½ inch) cubes and the tomatoes into wedges.
Marinate the beef with chicken powder, paprika powder, sugar, red wine, garlic, shallot, ginger and pepper corns. Let it marinate for about 30 minutes.
In your slow cooker, place the tomato at the bottom of the pot. Then, layer the marinated beef on top, along with the marinade sauce and all spices. Pour red wine into the pot, leaving 3 tbsp for later seasoning. Add water until it just reaches the level of the beef.
Cook the beef in the slow cooker on high heat for about 3 hours to 4 hours (depending on your slow cooker). If you're using the slow cooker mode of an Instant Pot, the cooking time will be around 3 hours and 30 minutes.
Once the beef reaches your desired level of tenderness, season the stew with fish sauce, sugar, chicken powder, and the leftover red wine. P/s: the broth should be slightly saltier than your desired flavor, as this will complement the pho noodles.
Add the slurry:- If using a slow cooker, add the slurry with a minimum of 30 minutes left in the cooking timee. This allows the raw flour taste to dissipate and the soup to thicken.- If using the slow cooker mode of an Instant Pot, add the slurry and switch to Sauté mode on low heat for 1-2 minutes. Follow the package instructions to prepare the pho noodles. After cooking, give them a rinse to remove excess starch.
Transfer the cooked noodles to a bowl. Pour the delicious broth over the noodles. Complete the dish with a sprinkle of thinly sliced onions, cilantro, or cleaved scallions. Enjoy!!