Peel and finely chop the garlic, chili pepper, and spring onion.

Cut the beef chuck into large bite-size pieces.

Combine the chopped garlic, chili pepper, spring onion, salt, black pepper, paprika, sweet chili powder, and Dijon mustard in a bowl.

Coat the beef pieces with the marinade and let them rest for 30 minutes.

Peel and thinly slice the 2 yellow onions.

Heat the vegetable oil in a heavy pot over medium-high heat.

Brown the marinated beef for 5 to 7 minutes, turning until the pieces are well colored.

Pour 150 ml of water into the pot and scrape up the browned bits.

Cover and simmer the beef over low heat for 45 minutes, until tender.

Add the sliced yellow onions, vinegar, and remaining 200 ml water to the pot.

Simmer uncovered for 20 minutes, stirring occasionally until the onions are soft and the sauce thickens.

Rinse the white rice in cold water until the water runs mostly clear.

Cook the white rice in water according to package directions, about 15 minutes.

Serve the beef yassa and onion sauce over the cooked white rice.