Place lentils in a saucepan with vegetable broth and bring to a boil. Cover and simmer for 15 minutes or until the water has evaporated and the lentils are soft. Drain and place in a food processor with oats. Add flour, onion flakes, bouillon, sugar, and spices in food processor and process until combined. Add 1 tablespoon at a time of extra vegetable broth if you need it.
In a large skillet, heat a bit of oil on medium-high heat and add the 2 Tablespoons minced onions. Saute until slightly browned. Add the filling mixture from the food processor to this and heat until browned.
Warm corn tortillas, fill with filling, and top with cilantro and onion.
You can try using a blender if you don't have a food processor, but I haven't tested it.