Season the beef pieces with 1½ teaspoon salt and 1½ teaspoon pepper.

Place a large dutch oven or heavy bottomed pot over medium heat. Add ⅓ cup of oil. Once the oil is sizzling, add as many pieces of beef that can fit in one single layer. Sear the beef until the pieces are golden-brown, about 3-5 minutes per side. Transfer on to a plate and continue searing the rest of the beef in batches. 

Transfer the beef to a plate and set aside.

Add the onions into the pot and cook until they have softened and are lightly golden, 10-12 minutes. 

Place the beef back into the pot with the onions and stir, then add the tomato passata, the remaining salt, and pepper and stir to combine.

Simmer over medium heat for about 3 minutes.

Reduce the heat to low and cover the pot. Cook on a gentle simmer until the sauce has thickened and the beef is very tender and falls apart, about 3 hours.

Serve the stracotto hot with matzo.