In a medium pot, saute onions and garlic in 1/4 cup water until translucent. Add spices, except garam masala and coriander, and cook for 2 minutes, adding more water if necessary to prevent sticking, burning or drying out. Add lentils, broth, tomato paste, tomatoes and coriander. Cover and turn heat to high. Once boiling, reduce to low and simmer for 15 minutes, or until lentils are cooked (they will expand and turn orange). Add garam masala and stir to combine. Cover and set aside for 3-5 minutes. Add salt and pepper to taste and serve.