- In a large saucepan over medium heat, soften the onions for 5 minutes in the oil. Add the rice and broth. Bring to a boil. Cover and cook for 30 minutes over medium-low heat or until the rice is tender and all the liquid has been absorbed. Add the salmon cubes. Cook uncovered for 5 minutes, stirring frequently, until the salmon begins to flake. Season with salt and pepper. Set aside.
- Meanwhile, in another large saucepan of salted boiling water, blanch the cabbage leaves for 5 minutes or until tender. Cool in an ice bath and drain. Pat dry with paper towels.
- Lay the cabbage leaves flat and, using a paring knife, trim the thickest section of the stem at the base of each leaf.
- Line a bowl with a 9-inch (23 cm) opening with 7 cabbage leaves, starting with the greenest leaves. Cover with one-third of the salmon mixture. Layer with 4 cabbage leaves. Cover with the remaining salmon mixture and the remaining 4 cabbage leaves. Press the stuffed cabbage into the bowl to create a rounded shape.
- In a small bowl, combine the broth and tomato paste. Set aside.
- Gently turn the stuffed cabbage out into a large skillet. Reshape, if needed. Pour the broth mixture into the skillet and place the cherry tomatoes around the cabbage. Season with salt and pepper. Bring to a boil. Cover and let simmer over low heat for 15 minutes or until the tomatoes burst and the cabbage is tender but still bright green.
- Gently cut the stuffed cabbage into wedges and serve with the cherry tomato sauce.