Soften the onions

• Peel the onions and slice them halfway down the center.
• Drop them into a pot of boiling water and cook until the layers soften and separate easily.
• Drain, let cool slightly, then separate the layers, keeping the outer shells intact and chopping the inner layers.

Make the plant-based filling

• In a bowl, combine the rice, lentils, chopped vegetables and the chopped onion cores.
• Drizzle in the olive oil and season with salt and pepper.
• Mix until evenly combined.

Prepare the tomato sauce

• Pour the tomato passata into a bowl and stir in a drizzle of olive oil and a pinch of salt.
• Spread a layer of the sauce over the bottom of a baking dish.

Stuff the onions

• Fill each onion shell with the rice and lentil mixture.
• Arrange the stuffed onions in the baking dish and spoon the remaining tomato sauce over them.

Bake

• Cover the dish and bake until the rice and lentils are tender and the onions are caramelized.
• Let rest a few minutes before serving.