Vegetarian Sheet Pan Tacos

Preheat oven to 425°F. Lightly oil one half of a large baking sheet and cover the other half with foil, folding up the middle edge to create a division. Place the whole poblano peppers on the oiled side of the pan.
Toss diced mushrooms and sliced onions with cumin, chili powder, cayenne pepper, and salt. Then spread the mixture evenly on the foil side of the baking sheet. Dot the top of the mushroom mixture with cubed butter (or olive oil). Bake for 12 minutes.
After 12 minutes, flip the peppers and toss the mushrooms, continuing to bake for an additional 5-6 minutes.
Remove peppers and place them in a covered container (a bowl with a plate or lid on top will work great!) and let them steam while the rest of the veggies continue cooking in the oven. At this time, toss the black beans and corn in with the mushroom mix, and bake for approximately 4 additional minutes.
Peel the poblano peppers by gently holding the stem and using the back edge of a knife to scrape the skin off. Once they're peeled, cut off the stems, slice down the middle to remove the seeds, and dice. Toss the poblano pieces with the mushroom mixture to complete the taco filling. Serve the filling with tortillas and toppings as desired. Enjoy!