Make the pickled onions. Combine ½ cup boiling water with ½ cup distilled white vinegar, 1 tablespoon sugar, and 1 teaspoon salt. Pour over the sliced red onions in a medium bowl and let sit for 30 minutes.

Preheat oven to 400 degrees F.

Toss together the sliced butternut squash with 2 tablespoon olive oil, 2 teaspoon chili powder, 1 teaspoon paprika, 1 teaspoon cumin, and ½ teaspoon oregano. Season with salt and pepper. Spread the squash on a baking sheet in an even layer. Roast for 15 minutes, flip and roast for another 10 minutes or until tender. Keep warm.

Make the salsa verde. Combine all of the ingredients together including ½ cup chopped cilantro, ½ cup chopped parsley, 2 tablespoon chives, 1 teaspoon lime zest, 3 tablespoon lime juice, ¼ cup toasted pine nuts, 1 tablespoon garlic, and 1 cup olive oil. Season with salt and pepper.

Heat 1 tablespoon olive oil in a non-stick saute pan over medium heat. Cook the halloumi until browned on both sides, about 3 minutes. Remove from heat and keep warm. In the same pan, saute the sliced pasilla peppers until charred, about 4 minutes.

Wipe the pan clean and heat the tortillas until softened.

Assemble the tacos. Fill the tortillas with the roasted butternut squash, halloumi, charred pasilla peppers, pickled onions, and salsa verde. Serve immediately.