In a large saucepan, combine 4 cups water, lentils, potatoes, onions, diced tomatoes, salt, garam masala, cumin and pepper. Cover and bring to a boil over high heat. Reduce heat to medium-low and simmer, covered, for 35 minutes. Stir occasionally. Add yellow peppers and simmer an additional 5 minutes.
Stir in cilantro and sprinkle almonds over top.