Preheat the oven to 450°In a medium pot, combine the quinoa, ½ cup of water (double for 4 portionand a pinch of salt; bring to a boil. Cover and let simmer, 14 to 16 minutes, until the quinoa is tender. Fluff with a fork.
While the quinoa cooks, halve the poblano peppers lengthwise; remove and discard the stems, ribs and seeds, then thoroughly wash your hands. Peel, halve and small dice the onion. Shuck the corn and cut the kernels off the cob. Roughly chop the cilantro leaves and stems.
In a large pan, heat a drizzle of olive oil on medium-high. Add the onions and spice blend; cook, stirring frequently, 1 to 2 minutes, until fragrant. Add the corn and cook, stirring occasionally, 2 to 3 minutes. Add the diced tomatoes and bring to a boil. Reduce the heat and let simmer, stirring occasionally, 6 to 8 minutes, until the sauce has thickened. Add the spinach and cook, 2 to 3 minutes, until wilted; season with S&P to taste.
Place the poblano pepper halves, cut sides up, in an oven safe baking dish, Divide the finished quinoa and vegetable sauce between the poblanos. Spoon the remaining sauce around the stuffed poblanos. Top each poblano with the panko and cheese.
Bake in the oven, 20 to 25 minutes or until the cheese and panko is golden brown. Divide the stuffed poblanos between your plates and garnish with the cilantro.