Preheat oven to 400ºF and spray a rectangular baking dish with oil or cooking spray.

Place half of the red onions in a small bowl with the lime juice and a small pinch of salt. Toss to coat and set aside.

Spread the enchilada sauce over the bottom of the baking dish. Place the poblanos on the sauce cut side up.

Heat the olive oil in a large skillet over medium-high heat. Add the remaining onions to the skillet with a pinch of salt. Cook until softened and starting to brown, about 4 minutes. Stir in the cumin, chili powder, and garlic; cook about 1 minute, until fragrant.

Add the corn, zucchini, and beans; cook for 2 minutes. Pour in the stock or water and bring to a simmer, then stir in the grits. The mixture should thicken after a minute or so; at that point, fold in 1/2 cup of cheese and season with additional salt to taste.

Stuff the poblano peppers with the vegetable mixture (or if your poblanos are kind of flat, spread the mixture onto them like you're layering a casserole). Sprinkle the remaining cheese over the stuffed peppers and wrap the dish tightly with foil.

Bake the peppers for 30 minutes covered, then 5 minutes uncovered. Top with the quick-pickled red onions and cilantro before serving.