In a heavy, 5-quart pot over medium heat, fry chopped onions, carrots, and cauliflower in olive oil until softening and translucent, about ten minutes.
Add minced garlic, 1/2 teaspoon of grated ginger root, and dry spices, and fry one minute longer.
Add red lentils, chicken, drained chickpeas, tomato paste, and salt, plus 3.5 cups water.
Bring to a boil, then reduce heat to low. Simmer, stirring occasionally, until lentils are completely softened and the stew has thickened, about 20 minutes.
Remove curry from the heat, and stir in fresh lemon juice from half a lemon.
Ladle over brown rice (if using) and top each serving with a spoonful of yogurt.