In a heavy pot or dutch oven heat the oil. Add onions and fennel seed. Saute over medium-high heat until the onions are translucent. Season with salt and pepper.
Add curry paste, minced garlic, ginger root, turmeric, and cinnamon. Cook over medium-high heat for 2 minutes to let the flavors combine.
Add chopped tomato and place the lid tightly on top. Continue to cook on medium-high heat for 3-4 minutes until the tomatoes begin to break down and form the sauce.
While the sauce is cooking, remove the skin from the chicken breasts, and cut each piece into chunks. I usually cut them crosswise into three large pieces, then cut each piece again, through the middle. If you don't have a knife sharp enough to do this, ask your butcher to help out with this step.
Add the chicken pieces and stir well, making sure the chicken is evenly coated with the sauce. Squeeze the lemon juice on the top. Turn the temperature to medium low and simmer covered for 20 minutes.
After 20 minutes add drained lentil soup, cubed potatoes. Season this layer lightly with salt and pepper.
Replace the lid, and continue to cook on medium-low for another 30-35 minutes until the chicken is done and the potatoes are fork tender.
uncover and sprinkle with chopped cilantro. Serve over Basmati rice.