Heat oil in a large sauté pan over medium heat until shimmering. Add cumin and oregano and cook until fragrant, about 1 minute. Add chile, onion, garlic, and 1 teaspoon of the salt and cook until onion is tender, about 7 minutes.
Add mushrooms and remaining 1/2 teaspoon salt and cook, stirring occasionally, until mushrooms are browned and tender, about 6 minutes.
Remove the pan from heat and stir in tomato, cilantro, and lime juice. Season with salt and freshly ground black pepper. Divide mixture among tortillas and serve with optional garnishes.