Heat the oil in a medium saucepan over medium heat. Add the onion and cook, stirring occasionally, until tender and evenly browned, about 10 minutes. Add the ginger, garlic, chile, and turmeric, and stir to incorporate, then stir in the masala and salt and stir to evenly coat the onions. Add the tomato and cook, stirring often, until the tomatoes soften and meld with the other ingredients, 2 to 3 minutes. Set aside.
Put the rinsed lentils in a large saucepan and add 2 cups of water. Add the onion/spice mixture and the chopped vegetables, stirring to mix with the lentils. Bring the water just to a boil, then reduce the heat to medium-low, cover, and simmer until the lentils and vegetables are very tender, 30 to 40 minutes, stirring occasionally. The water should not boil vigorously; reduce the heat if needed. (You can use a multicooker according to manufacturer’s instructions, cooking for about 12 minutes.) When tender, set aside to cool for 10 to 15 minutes, then use an immersion blender to purée the mixture until smooth, or purée in a blender. If the mixture is quite thick, add a bit more water. Set aside to reheat before serving.
Grill or broil the poblanos until lightly charred but still holding their shape, 3 to 4 minutes, using tongs to carefully turn the chiles a few times. Remove 4 of the chiles and set aside. Continue roasting the remaining chile until it is more charred and tender, 3 to 5 minutes longer. Transfer this chile to a bowl, cover with plastic wrap or foil, and let sit until cool.
Remove the skin, core, and seeds from the tender chile and finely chop it. Put the chopped chile in a bowl with the quinoa, corn, onion, and a good pinch of salt and stir well to evenly mix.
Cut the remaining chiles in half lengthwise through the stem. Remove and discard the seeds and ribs, and use a small knife to cut away most of the tough core while leaving the stem intact to help hold the chile together.
Preheat the broiler again. Set the lentil purée over medium-low heat to warm for serving.
Fill each poblano half with some of the quinoa mixture, mounding it slightly, and set them in a baking dish. Toss the cheeses together in a small bowl and top the stuffed chiles with cheese. Broil until the cheese is melted and the chiles slightly warmed, about 3 minutes.
To serve, spoon some of the lentil purée onto each plate and top with two halves of the stuffed poblanos. Top each with a few cilantro leaves and serve right away.