Rinse lentils and add into a saucepan or pot and cover with water, making sure water is at least 2" above lentils. Heat over medium high heat boiling. Cover and reduce heat to simmer. Cook for about 25 minutes, stirring at least once, or until lentils are tender to your liking. Drain in a fine mesh strainer.
Add oil, onion, green pepper and garlic to a skillet and heat over medium high heat until onions are translucent and green peppers are tender. Add chili powder, paprika, salt and pepper.
Stir in tomato sauce, mustard and brown sugar and mix well. Add cooked and drained lentils and heat over medium low heat until heated through and hot.