Preheat the oven to 180º C / 375º F.
Peel the onions and remove both ends. Make a cut from top to bottom, reaching the middle of each onion- do not cut all the way through!
Boil the onions until tender, about 15-20 minutes. Rinse with cold water to stop the cooking process, then carefully separate each layer.
In a large bowl, combine the rice, vegan ground beef, chopped tomatoes, parsley, garlic, pine nuts, tomato paste, lemon juice, olive oil, dates, pomegranate molasses, salt, and pepper.
Take one layer of onion and place a small amount of the rice mixture in the bottom half, then roll it upright. Repeat with the remaining onion layers and filling.
Arrange the stuffed onions in a large oven-safe skillet, pot, or baking tray, seam side down.
In a separate bowl, mix the sauce ingredients. Pour the sauce over the onions, cover with parchment paper, and then aluminum foil.
Bake for about 1 hour and 30 minutes. Remove the cover and optionally broil for an additional 10 minutes for that nice deep golden color. Be careful as to not overcook and dry out the onions.
Serve warm and enjoy!
