Put the lentils, cinnamon stick, and 7 cups of water in a 6-quart Dutch oven. Bring to a boil over medium-high heat; cook for 5 minutes
Meanwhile, rinse the rice in 2 to 3 changes of cold water until the water is no longer cloudy. Stir the rice and 1/2 Tbs. salt into the lentils and return to a boil; reduce the heat to medium low, cover the pot, and simmer gently, stirring occasionally and adjusting the heat as necessary to maintain a gentle simmer, until the rice and lentils are tender, 13 to 15 minutes more. Drain in a colander and shake well to remove excess water. Remove and discard the cinnamon stick.
Wipe out the Dutch oven. Return it to medium heat, add the butter, and let it melt until foaming. Add the onion, jalapeño (if using), and 1/4 tsp. salt and cook, stirring often, until the onion is softened and translucent, 4 to 6 minutes. Stir in the curry powder, ginger, and garlic; cook, stirring, until fragrant, 1 to 2 minutes. Add the rice mixture and cook, stirring, until well mixed and heated through, 3 to 5 minutes. Stir in the peas and lemon juice and season to taste with salt and pepper. Add the salmon and cilantro and toss gently to combine.
Serve sprinkled with the chopped egg and with the chutney on the side.