In the 4-quart pot, heat the butter and canola oil over medium-low heat. Add the ginger, garlic, and slivered onions, cooking and stirring until wilted, about 10 minutes.
Stir in the drained lentils, add the vegetable broth, and bring to a boil over high heat. Reduce the heat to around medium and simmer uncovered for about 20 minutes, until the lentils are soft but not mushy, stirring occasionally. Skim off the foam as it rises to the top.
Stir in the tomatoes and parsley. Continue to cook and stir for another 15 minutes. The lentils should be very soft. Add salt and pepper to taste. Serve hot or at room temperature.